Enhancing RAP-Based Pavement Layers with Industrial Byproduct Blends for Improved Performance and Sustainability

Enhancing RAP-Based Pavement Layers with Industrial Byproduct Blends for Improved Performance and Sustainability | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Enhancing RAP-Based Pavement Layers with Industrial Byproduct Blends for Improved Performance and Sustainability ranjitham Mariyappan, Jeyapriya Subanantharaj Palammal, Soundara balu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6961746/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 5 You are reading this latest preprint version Abstract The recycling of asphalt pavement has become a widely accepted practice in the transportation industry, driven by environmental, economic, and social benefits. Reclaimed Asphalt Pavement (RAP) consists of materials obtained from existing asphalt pavements that are no longer viable for reconstruction or resurfacing. Before RAP can be reused in construction, especially in base and subbase layers, it must undergo laboratory testing to verify its suitability. While many transportation agencies have embraced the use of RAP in unbound layers, its application is often restricted due to its relatively low strength, necessitating the use of stabilizing additives. To overcome this limitation, recent research efforts have focused on enhancing the performance of RAP by blending it with industrial byproducts. This study investigates the effectiveness of combining RAP with cement, fly ash, and ground granulated blast furnace slag (GGBS) to produce sustainable, high-performance pavement materials. Laboratory tests were carried out to assess the physical characteristics and mechanical performance of various mix combinations. A key focus of this study was to evaluate a mixture containing 50% RAP and 50% virgin aggregate (VA), stabilized with 7% cement. This specific blend demonstrated a compressive strength of 4.5 MPa, indicating its suitability for pavement applications. Among the various combinations tested, the 50:50 RAP:VA mixture with cement showed superior performance. It not only met the required strength criteria but also offered significant cost and environmental benefits by reducing the need for natural aggregates and lowering overall construction expenses. Incorporating RAP with stabilizing agents such as cement, fly ash, and GGBS significantly enhances the strength and durability of the final product, making it a viable and sustainable option for modern pavement construction. As the transportation sector increasingly emphasizes sustainability, integrating recycled materials like RAP into infrastructure projects will be critical in achieving long-term environmental goals and building resilient road systems. Reclaimed asphalt pavement Virgin aggregate Cement Fly ash GGBS base Sub base course Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 1. Introduction and background The escalating costs, rising demand, and shortages of VA have led to an increased exploration of alternative materials for asphalt pavement. In India alone, approximately 15,000 tonnes of VA are needed for every kilometre of a national highway, as noted by (Aurangzeb and et al 2014 ). However, the concept of reusing old pavement materials is not widely embraced in India, leading to the majority of demolished pavement materials ending up in landfills, which complicates the issue of environmental waste(Arshad M, Ahmed MF 2017) The construction of roads not only requires vast quantities of natural resources globally but also responsible for about 22% of the world's total energy consumption, 25% of fossil fuel usage, 30% of air pollution, and greenhouse gas emissions. However, the production of RAP generates a significant amount of waste, reaching billions of tons annually, as highlighted by the Federal Highway Administration (2008). Furthermore, there is a growing concern on utilizing RAP to mitigate environmental impacts and conserve natural resources worldwide. RAP is essentially a mixture of aggregate bound with asphalt. Research has been conducted on the current challenges of utilizing RAP in pavement base and subbase layers, as highlighted by Milad et al. ( 2020 ). At the University of California, Berkeley, researchers are developing innovative methods to extract and recycle asphalt binder from RAP using microwave technology. This approach could enhance the quality and consistency of RAP, making it more suitable for high-performance asphalt mixtures, as detailed by Bleakley and Cosentino ( 2013 ). Currently, there is an urgent requirement to classify the available RAP for its subsequent essential applications in road construction. Research by Arshad M and Ahmed ME in (2017) highlighted that RAP exhibits good thermal stability, meaning it performs well across a wide temperature range. This stability is attributed to the asphalt binder in RAP being less affected by temperature fluctuations compared to new asphalt binder. Hence, replacing virgin asphalt (VA) with 100% RAP leads to lower strength but increased resistance to creep and permanent deformations. Nevertheless, RAP can be effectively used in conjunction with natural aggregates, blended with cement, or combined with other additives such as fly ash or geocells, as demonstrated in various studies of (Saride et al. 2010). This research explores the importance of blending RAP with fly ash, cement, and (GGBS) to achieve specific properties of VA. For instance, blending RAP with cement is a common strategy in pavement construction to enhance the strength and durability of the pavement (Taha et al. 1999 ) When cement is introduced into fine fractions of RAP, it reacts with the mineral components as well as with the residual asphalt binder, affecting the material's strength and durability. The reaction is mainly influenced by amorphous silica, mineral fines, and aged asphalt. In the case of amorphous silica present in the fine RAP particles, it can engage in pozzolanic reactions with cement to produce calcium silicate hydrate (C-S-H) gel, which increases cohesion and strength. The cement serves as a binding agent, securing the RAP particles together and boosting the pavement's overall strength. This approach has been found to significantly improve the performance of pavement in terms of resistance to rutting, cracking, and fatigue. Such enhanced performance results in reduced maintenance costs and a longer lifespan for the pavement, making it a popular choice in pavement construction, expected to grow in the coming years (Ebrahim Abu El-Maaty Behiry 2013). The addition of fly ash increases the strength of the mix, primarily depending on the type, curing period, and nature of the activator used (Jayakody et al 2019 ). This is because fly ash possesses pozzolanic properties. In the presence of moisture, fly ash reacts with calcium hydroxide to form cementitious compounds. These reactions enable fly ash to enhance the strength and durability of asphalt pavement (Athanasopoulou 2014). Furthermore, fly ash particles are very small, typically less than 10 microns in size, making them an effective mineral filler in asphalt mixtures (Saride et al. 2016). These materials fill the gaps between larger aggregate particles, thereby improving the packing density of the mix. Additionally, fly ash increases the strength and stiffness of the both base and subbase layers, reducing issues such as rutting and fatigue cracking that can occur due to dynamic loads. When blended with mixtures, calcium oxide reacts with the silica present in RAP, forming hydrated products that increase the strength and stiffness of the pavement layers. The availability of silica in RAP may influence the whole study, subject to its nature and reactivity. When the silica is of amorphous nature, it can easily take part in pozzolanic reactions, promoting cementation when RAP is incorporated in cement-based products such as recycled asphalt concrete or asphalt-treated base layers. This can enhance bonding, strength, and durability in the resultant mix. GGBS, a by-product of the iron and steel industry, has been widely utilized as a partial substitute for Portland cement in pavement construction. Its high resistance to chemical and sulphate attacks contributes significantly to the increased durability of pavements. Additionally, GGBS enhances the resistance to alkali-silica reaction, a leading cause of pavement deterioration. By adding GGBS, pavements can also become stronger, as it aids in the formation of additional calcium silicate hydrates (C-S-H) in concrete. RAP is a mixture of asphalt binder and aggregate, both of which are known for their strength and durability. RAP is a granulated composite geomaterial that exhibits high activity even under normal atmospheric conditions (Abraham SM, Ransinchung GDRN (2018). The use of RAP not only reduces overall construction costs but also ensures the efficient use of available resources. Studies have shown that the incorporation of RAP into pavements, up to a maximum of 30% in base layers, has been successful. However, achieving the desired performance with RAP content above 30% requires careful selection of supplementary additives. Successful replacement of VA with RAP has been attributed to factors such as the binder content, well-graded aggregates, and effective mix design. The application of RAP materials in pavement construction offers benefits like lower material costs, conservation of aggregate resources, reduction in disposal costs, and elimination of waste from landfills (Khan et al 2020 ). The usage of RAP as an alternative to virgin materials is very environmentally friendly, especially in lowering greenhouse gas (GHG) emissions. Virgin asphalt manufacturing involves energy-intensive processes such as raw material extraction, transportation, and heating of raw materials like aggregates and bitumen. All these processes release considerable amounts of CO₂. Conversely, RAP minimizes the requirement for new raw materials by recycling old asphalt, reducing energy consumption and minimizing the emission related to the processing of materials. Furthermore, using RAP in pavement construction eliminates the need for landfilling aged asphalt, avoiding methane and other pollutants release from decomposing waste materials. The transportation emissions are also minimized as less virgin aggregate needs to be extracted and transported over long distances. Additionally, the application of RAP in warm mix asphalt (WMA) technologies also reduces emissions further by allowing the production of asphalt at temperatures lower than conventional methods, consuming less fuel and less air pollution. In general, incorporating RAP into asphalt mixture results in a greener construction practice through natural resource conservation, minimized carbon footprints, and the advancement of circular economy concepts in road construction. Storage and handling of RAP materials pose some challenges. One of the major issues is keeping the quality of the RAP intact over a period of time, as it is prone to contamination with extraneous materials such as soil, debris, or organic material, which can reduce its performance during subsequent use. It is reported in a study that RAP contamination may have considerable impact on the mix's general properties, e.g., binder content and aggregate gradation, to make it more difficult to attain the preferred asphalt mixture. Furthermore, inappropriate storage can lead to the degradation of the RAP's quality, especially if exposed to excessive moisture or harsh weather conditions, which would impact its functionality to mix well with virgin material when repaving. Kim et al. ( 2018 ) identified in their research that variability in RAP materials may cause inconsistency in mix performance, which may cause construction quality control to be challenging. These issues can cause inconsistencies in the final quality of the pavement. To ensure the quality and usability of RAP materials in new asphalt mixtures, it is crucial to implement proper storage facilities, effective quality control measures, and accurate testing procedures. Various evaluations have been conducted to assess the mechanical and engineering characteristics of both aged and fresh RAP, along with their combinations with VA. These assessments include sieve analysis, specific gravity measurement, flakiness index, elongation index, water absorption, and pH analysis. Additionally, impact, abrasion, and compressive strength tests have been carried out to examine the performance of different pavement mix compositions. This study primarily focuses on identifying the optimal proportion of RAP blended with cement, fly ash, and GGBS for pavement base layers. The chemical composition of RAP materials was analyzed using X-ray fluorescence (XRF) to detect primary minerals and potential impurities. Fourier Transform Infrared Spectroscopy (FT-IR) was utilized to examine the chemical properties of the asphalt binder, providing insights into oxidation, aging, and the presence of additives. Moreover, key engineering parameters such as optimum moisture content (OMC), maximum dry density (MDD), unconfined compressive strength (UCS), California Bearing Ratio (CBR), indirect tensile strength (ITS), and Marshall Stability were investigated to determine the feasibility of RAP mixes for pavement construction. 2. Material used 2.1. Collection of materials The primary ingredients utilized in various tests include Ordinary Portland Cement (Grade 33), Fly Ash (Class C), GGBS, RAP), and VA. The primary properties of these raw materials were initially assessed through preliminary tests according to both ASTM and Indian Standards. The Ordinary Portland Cement (Grade 33) was sourced from a cement factory in Chettinadu. The impact of RAP on cement properties varies significantly, dependent on factors such as RAP quality and quantity, cement composition and curing conditions, and cement specific gravity (2.5 to 3.5). The concrete produced meets the IS 4031-3 standard with a soundness value of 0.4mm. Fly Ash, produced in Mettur Thermal Power Plant, Mettur, with coordinates 11°30'17.1936"N 77°14'18.2256"E, was collected in the wet state and stored in the open to reduce moisture content before being processed in the lab. The collected raw materials were then transported to the laboratory, where they were placed in a dehumidified environment to further reduce moisture content prior to being subjected to characterization tests. According to IS: 2386 (PART III), fly ash typically has a specific gravity of 2.28. Flyash,waste product of coal burning in thermal power facilities, is an important component of asphalt mixtures due to its contribution to their performance and sustainability. As a mineral filler or modifier, fly ash increases the strength and durability of the mixture, rendering it more resistant to rutting, fatigue cracking, and moisture damage. It also increases workability, enabling more effective compaction and fewer air voids, which result in longer pavement life. GGBS, on the other hand, is a by-product of blast furnace melting, rapidly cooled (e.g. by immersion in water), and possesses a specific gravity of 2.85 and soundness value of 0.3mm, all satisfying IS 4031-3 standards. Recycled Aggregate (RAP), collected from various sites in Sathyamangalam, Erode district, between 11°30'17.1936"N and 77°14'18.2256"E, about 10 tons from four different locations were collected for the study. Virgin Aggregate (VA), on the other hand, was obtained from a construction site at the Bannari Amman Institute of Technology College in Erode district, with coordinates 11.4986°N and 77.2743°E. According to Tighe SL et al. (2015), the use of VA in construction projects plays a crucial role in enhancing the mechanical properties of concrete, as their original nature often leads to superior strength and durability. The color of RAP changes from dark and grey in wet conditions to a lighter grey in dry conditions, and it does not appear black, but rather slightly bitumen-coated. This observation aligns with the findings of Giani MI et al. ( 2015 ), who noted similar color variations in RAP materials depending on moisture levels, indicating potential impacts on workability and compaction. The physical characteristics of RAP were also determined through basic laboratory tests. Studies by Al-Suhaibani and Mamlouk ( 2019 ) emphasize that laboratory evaluations of RAP are fundamental for assessing its potential as a substitute in concrete mixes, particularly for its strength and gradation properties. 2.2 Methodology For enhanced strength and hardness of concrete, various mix proportions of VA and RAP were used to create test mixes. They were tested both with and without cementing material like OPC, Class C Fly Ash, and GGBS to find their effect on the mechanical characteristics. The research was interested in how different proportions of RAP and VA, when stabilized with these binders, impacted the strength and long-term behavior of the concrete. A systematic approach was followed to develop blend ratios from fully recycled aggregates to fully virgin aggregates, allowing for a thorough performance evaluation. Five particular blends were tested: 100% RAP, 75% RAP with 25% VA, 50% RAP with 50% VA, 25% RAP with 75% VA, and 100% VA. Stabilizers were added to the blends in an effort to maximize durability and mechanical strength. The stabilizers used were OPC, which enhances early strength gain and structural stability; Class C Fly Ash, which enhances workability, durability, and long-term strength and minimizes permeability; and GGBS, an industrial byproduct, which enhances durability, reduces heat of hydration, and boosts sulfate resistance. By incorporating these stabilizers, the research sought to create an ideal RAP-VA mixture for sustainable and high-strength concrete applications. Efficient blending is essential in deciding the right RAP content in asphalt mixtures, as it influences the interaction between aged RAP binder and virgin binder. Inefficient blending may result in improper binder content calculations, causing mixtures to be too stiff or too soft, which undermines pavement performance. Huang et al. (2014) examined the efficiency of blending RAP using rheological properties and molecular weight distributions. Their research showed that longer mixing time and higher temperature improved blending between virgin binder and RAP to a maximum blending ratio of slightly less than 80%. This result highlights the need to optimize mixing conditions to enhance blending efficiency. They concluded that an increase in mixing time and temperature resulted in more blending in the RAP/RAS mixture. Nevertheless, mobilization rate of RAP binder reduced with an increase in percentages of RAP, which shows that not all aged binder becomes active in the mix. These stabilizers were added to the concrete mixture in different proportions of 3%, 5%, and 7% of the weight of the entire mix. The main aim of this stabilization was to counteract possible weaknesses due to the addition of RAP, including lower bonding strength and increased moisture susceptibility. Besides, the stabilizers also helped in enhancing cohesion, compressive strength, and durability in general to ensure that the produced concrete would be suitable for performance requirements across a range of structural applications. RAP-VA mixes were evaluated using an extensive set of tests to evaluate their physical, mechanical, and durability properties. The purpose of these tests was to find the ideal blend of RAP-VA and the most suitable cementitious stabilizer dosage to achieve improved pavement performance. Physical characterization of aggregates was done by sieve analysis, which identified the particle size distribution to ensure that the gradation satisfied the specifications of base layers. Specific gravity tests enabled quantification of RAP and VA relative density, impacting mix design and compaction (AASHTO 2021). The flakiness and elongation index tests were conducted to determine aggregates' shape characteristics, as flaky or elongated particles may impair interlocking and compaction. Water absorption tests evaluated the aggregates' susceptibility to moisture, which is vital for mix durability, particularly in mixes containing RAP. The pH test was performed to assess the alkalinity or acidity of the aggregate mix since high pH levels can affect the hydration process of cementitious binders. To find out the mechanical resistance and degradation strength, impact and abrasion testing was conducted. The Aggregate Impact Value test assessed the sudden impact resistance of aggregates, an important parameter of base courses experiencing dynamic loads. The Los Angeles Abrasion test determined RAP-VA blends' resistance to wear such that they remained capable of facing repeated traffic. Compressive strength tests gave information about the capacity of stabilized RAP mixtures to withstand axial loads, which is critical for pavement longevity. The Unconfined Compressive Strength (UCS) test, performed on specimens with different RAP content and different dosages of stabilizer (3%, 5%, and 7%), showed how cementitious materials improved cohesion and load-carrying capacity. Increased UCS represented enhanced stabilization, whereas decreased UCS represented the necessity for optimization of binder content. With respect to performance-based testing, the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) tests were performed to quantify the optimal moisture and compaction values for maximum strength. The California Bearing Ratio (CBR) test was employed to evaluate the resistance to traffic loads of the RAP-VA mixtures, which is essential for their base layer applicability. Increased CBR values were representative of greater strength and traffic load deformation resistance. The Indirect Tensile Strength (ITS) test tested the tensile characteristics of the mixes, which are critical to avoiding cracking and fatigue failure. Finally, the Marshall Stability test was conducted to determine the load resistance of the RAP-VA blends to deformation, ensuring that the mixture would be structurally sound under vehicular stresses. Results of these tests altogether informed the choice of the best RAP percentage and stabilizer dose so as to strike a balance between sustainability and performance for pavement use. 2.3 Graphical Methodology` 3. Material characterization 3.1 Reclaimed Asphalt Pavement (RAP) And Virgin Aggregate(VA) The physical characteristics of RAP and VA were assessed to make sure that satisfy the fundamental requirements set by the Indian codes. This evaluation included tests such as sieve analysis, Specific gravity, Flakiness Index, and Elongation Index (Augusto Cannone Falchetto 2019). Moreover, the ability of RAP to absorb water and its pH levels were also checked. The proportion of different particle sizes in RAP can significantly affect its performance when added to new mixtures. 3.1.1 Gradation analysis of RAP Usually, the particle size distribution of RAP is coarser than that of VA because the asphalt binders deteriorate as the pavement ages (De Lira RR et al. 2015 ). To measure the size distribution of RAP, sieve analysis was performed in both old RAP (stored for months) and newly RAP (the pavement material was shortly after its installation), along with VA according to IS: 2386 (PART II) to calculate the parameters of Uniformity Coefficient (Cu) and Curvature Coefficient (Cc). Tables 1 and 2 present the results of the sieve analysis for both the aged and newly damaged RAP. It is essential to carefully control and modify the particle size distribution of RAP to ensure that it matches the requirements of the new asphalt mix design for optimal performance. Table 1 Gradation analysis of Old RAP Sieve size(mm) Mass of soil retained (g) Percent mass retained (g) Cumulative percentage retained (%) Percentage finer (n) 40 0 0 0 100 20 226 22.6 22.6 77.4 12.5 415 41.5 64.1 35.9 10 147 14.7 78.8 21.2 4.75 172 17.2 96 4 0.1 40 4 100 0 1000 100 Table 2 Gradation analysis of New RAP Sieve size(mm) Mass of soil retained (g) Percent mass retained (g) Cumulative percentage retained (%) Percentage finer (n) 40 0 0 0 100 20 160 16 16 84 12.5 250 25 41 59 10 100 10 51 49 4.75 390 39 90 10 0.1 100 10 100 0 1000 100 From above Fig. 1 it is clear that Sieve analysis of RAP typically reveals a particle size distribution that indicates the quality and suitability of the material for reuse in asphalt mixtures. In a typical result, the largest sieve size (40 mm) shows 0% weight retained, with a gradual increase in weight retained as the sieve size decreases. The particle size of RAP has a considerable impact on the behavior of asphalt mixtures subjected to repeated loading. Coarse RAP particles can improve aggregate interlock, enhancing load distribution and structural strength. On the other hand, fine RAP particles raise the surface area covered with aged binder, which can result in greater stiffness and lower fatigue resistance as a result of poor blending with virgin materials. For instance, at the 12.5 mm sieve, approximately 35.9% of the material is retained, while the 10 mm sieve retains about 21.2%. These results are crucial for determining the gradation of RAP and ensuring it meets the specifications for incorporation into new asphalt mixtures, ultimately contributing to sustainable construction practices. Changing the gradation of RAP can make a significant difference in the durability and workability of the asphalt mixture. For coarser gradation, usually occurring with older RAP, greater particles make the mixture stiffer, more difficult to compact, and less workable because of increased friction between the particles. This can create challenges in ensuring good compaction when the asphalt is installed, resulting in problems such as a non-level surface. Conversely, finer gradation, which commonly exists in newly broken RAP, can enhance workability through increased lubrication between aggregates, which makes it easier to compact and results in a smoother surface. In terms of durability, coarse gradation is likely to have a negative impact, in that large particles tend to compromise adhesion between asphalt binder and aggregates. This might contribute to increased void content in the mix, lower density, and increased permeability, ultimately causing earlier wear and greater vulnerability to water damage. Conversely, finer gradation enhances binder adhesion and yields higher density, which minimizes the voids and enhances the mix's resistance to moisture damage, cracking, and fatigue. The improved binder coverage also enhances the overall resistance to rutting and cracking, which helps to make the asphalt pavement more durable. Moreover, gradation influences the mix's consistency and uniformity. Coarse gradation can cause inconsistency in the behavior of the material, making it more difficult to have an even distribution of binder, whereas finer gradation provides more uniform performance because of the more even particle size. Additionally, a finer gradation will usually use less binder to provide adequate coating of the aggregates, which can result in cost savings. In exceeds 50%, the gradation of RAP is very influential in establishing workability, toughness, and total performance of asphalt mix, finer gradation, in most instances, tending to produce favorable mix properties as well as sustained performance. 3.1.2 Water absorption test of RAP The absorption test for RAP is a method used to evaluate the porosity of RAP or asphalt materials. This test assesses the ability of RAP to withstand adhesive strength under heavy loads, helping to determine its capacity to absorb water. This absorption can significantly impact the material's durability and performance. Durability of materials was conducted to measure the amount of water absorbed by RAP, falling within the range specified by IS:2386 (PART I-VII) from 0.1 to 2. A lower absorption percentage indicates a denser, more durable material, whereas a higher percentage suggests a more porous material that may be more vulnerable to damage from water and other environmental factors. The water absorption values for old and new RAP were found to be 1.5 and 1.2, respectively. Typically, materials with water absorption (VA) of 0.65–2.0%, falling within the range of 0.5–2.0%, are considered to be of higher quality(Arulrajah and piratheepan 2014) This is because they are free from aged binders and contaminants, offering a more uniform and predictable performance in asphalt mixtures. However, the presence of bitumen in RAP can affect its water absorption. The surface of the aggregate also plays a role in this phenomenon. According to Brown et al. ( 2009 ), aggregate surface texture can significantly influence binder adhesion and moisture resistance in asphalt mixtures. On the other hand, RAP is more likely to exhibit higher absorption values, ranging from 1.5–4.5%, due to the aging of asphalt binders and potential degradation of the original aggregates (Pavement Recycling Guidelines, FHWA, 2011). This increased absorption in RAP can alter the overall binder content of the mix, necessitating adjustments to ensure an adequate supply of new binder for proper coating and bonding (Mcdaniel and Anderson 2001 )While virgin aggregates absorb less water, reducing the risk of moisture-related issues (Roberts FL et al 1996 ), the higher water absorption of RAP requires careful consideration in mix design to mitigate potential moisture damage (Huang et al 2005). Therefore, while RAP contributes to sustainability in asphalt production (Hansen K R, Copeland A 2017), its higher and variable water absorption values demand meticulous management in mix design to ensure the pavement performs optimally (Shirodkar et al 2011 ). 3.1.3 Elongation and flakiness test of RAP The elongation index of an aggregate is a key measure that determines the percentage of particles, by weight, whose length exceeds four-fifths of their mean dimension. According to (Mohammadinia A et al 2016 ), elongated aggregates may compromise the structural integrity of pavements, as they tend to break under heavy loads due to their slenderness. This property is of particular interest when comparing RAP and (VA). For calculating the elongation properties, RAP and VA particles are subjected to standard procedures, such as the use of a 63 mm sieve, which retains particles larger than 6.3 mm. In compliance with IRC (Indian Roads Congress) recommendations, the elongation index for various types of pavements is typically limited to 25%. Higher values may indicate a potential for material instability under dynamic loads, a point echoed by (Khanna and Justo 2011 ). However, before conducting the elongation index test, a flakiness test is crucial, as flaky particles can introduce inherent weaknesses in the aggregate structure. According to Airey et al. (2008), flaky particles, due to their thin structure, are more prone to breakage, potentially leading to material failure when subjected to heavy traffic or load stresses. The properties in Table 3 , which compare the flakiness and elongation indices of RAP and VA, underscore the significance of these tests in ensuring material durability. As supported by Roberts et al. ( 1996 ), understanding the flakiness and elongation of aggregates is essential for optimizing the performance of pavements, particularly when recycled materials like RAP are used. Table 3 Flakiness and Elongation index of RAP compare with VA Properties Old RAP New RAP VA IRC recommendation Flakiness index 33.76% 40.57% 18.11% 35%(IS 2386 (Part 1):1963 Elongation index 23.11% 25.4% 17.11% 25% Table 3 reveals that the flakiness index of RAP is generally higher compared to VA. This is because VA, with their more uniform, cubical shapes resulting from controlled processing methods, typically exhibit lower flakiness index values, ranging from 10–25% [54]. Studies by Sivakumar and Jain (2010) also support that virgin aggregates exhibit a more cubical shape due to precision in manufacturing processes, contributing to their lower flakiness indices. On the other hand, RAP's flakiness index values can range from 20–40%, due to the milling and crushing processes used in its recovery, which often produce more flat and elongated particles. This observation is in line with Croteau and Tessier (2008), who emphasized the impact of milling operations on the shape of RAP particles. According to Kandhal P S and Mallick R B (1997), flakiness in RAP can adversely affect the compaction, stability, and load-bearing capacity of asphalt mixes, potentially leading to pavements that are weaker and less durable. However, it's important to note that the flakiness index values are within the acceptable range according to IRC guidelines, which means that careful adjustments in mix design and compaction techniques are necessary to ensure optimal pavement performance. Studies by Huang et al. (2005) also indicate that although RAP has a higher flakiness index, mix design adjustments can mitigate the effects. Additionally, the elongation index of RAP is typically higher than that of virgin aggregates. VA usually have lower elongation index values, typically ranging from 5–20%, due to their controlled production processes that yield more cubical and uniformly shaped particles. In contrast, RAP often exhibits higher elongation index values, typically ranging from 15–35%, as the milling and crushing processes involved in its recovery can produce more elongated particles. González-León et al. ( 2019 ) also observed that the elongation index in RAP influences compaction behavior due to elongated particles. These higher elongation values in RAP can negatively impact the compaction and interlocking characteristics of asphalt mixes, potentially reducing their stability and load-bearing capacity. Elongated particles in RAP can lead to increased voids and decreased structural integrity, necessitating careful adjustments in mix design and compaction practices to ensure the performance of pavement and durability. 3.1.3 Specific gravity test of RAP RAP is primarily defined by its rigidity and strength rather than its elasticity or deformability. However, these characteristics are influenced by factors such as the age and condition of the original pavement. As shown in Table 4 , the specific gravity of both old and new RAP aligns with the range specified in IS: 2386 (Part III). Specific gravity, which varies based on material composition and manufacturing conditions, typically ranges between 2.0 and 2.4 for RAP. This is comparable to the specific gravity of virgin asphalt (VA) mixtures, further supporting RAP's suitability as a material in road construction. Table 4 Specific gravity of RAP combinations with VA Mix proportions 100% RAP 75%RAP + 25% VA 50%RAP + 50% VA 25%RAP + 75% VA 100 VA As per IS: 2386(PART 1) Old RAP 2.33 2.59 2.65 2.62 2.65 2.5 to 3 New RAP 2.26 2.09 2.50 2.60 2.5 to 3 The specific gravity of the RAP may be affected by gradation, the type and quantity of binder, contaminants, or other materials. The specific gravity may also change over time due to aging or weathering. The specific gravity measurements of the old RAP ranged from 2.33 in the 100% RAP mix to 2.65 in the 50% RAP + 50% VA and 100% VA mixes, consistent with the recommended range of 2.5 to 3. Likewise, the specific gravity of the new RAP varied from 2.09 in the 75% RAP + 25% VA mix to 2.60 in the 25% RAP + 75% VA mix. Though the older RAP values generally complied with the specified requirements, the new RAP registered some variations, especially in the 75% RAP + 25% VA mix that had the lowest specific gravity of 2.09. The variations point out that the addition of VA to the mix enhances the general density and stability, especially in the 50% RAP + 50% VA and 25% RAP + 75% VA mixes. The results indicate that the use of a balanced ratio of RAP and VA improves the quality of the mix and also ensures standard specification compliance. 3.1.4 pH value of RAP The pH values of both old and new RAP are measured at 8.6 and 8.5, respectively, aligning with the acceptable range specified for asphalt materials. As per IRC 015-2011, which provides guidelines for materials in road construction, the optimal pH range for asphalt is 8.6 to 8.9 to ensure stability and durability. Ayan et al. ( 2014 ) underscore the significance of evaluating the chemical and physical properties of recycled aggregates to ensure their compatibility with virgin materials. Their research highlights that understanding chemical characteristics, such as pH, is crucial for maintaining the integrity and performance of asphalt mixtures. The results indicate that both old and new RAP exhibit similar chemical properties to virgin asphalt (VA), particularly in terms of alkalinity, confirming their suitability for reuse in road construction. 3.1.5 Chemical composition analysis using X-ray Fluorescence (XRF) test X-ray Fluorescence (XRF) analysis of RAP is a critical analytical method employed to ascertain the elemental content of its aggregates and binder. The test assists in the identification of the major oxides including silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), calcium oxide (CaO), and iron oxide (Fe₂O₃), which affect the mechanical characteristics of the pavement material. Moreover, XRF is capable of identifying trace metals such as lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr), which could be signs of contamination from industrial or traffic sources. The analysis also offers information on binder aging through the detection of elemental changes that are indicative of oxidation and degradation over time. Knowledge of the chemical composition of RAP from XRF analysis is important for maximizing its reuse on road construction, maintaining quality control, and reducing environmental effects. This study was conducted at the Ceramic Research Centre in Chennai. Common minerals identified include silica, aluminium oxide, sulfur trioxide, potassium oxide, calcium oxide, and various clays, all of which significantly impact the material's properties and performance. As reported by Kumar et al. (2017), the presence of these minerals in RAP plays a critical role in determining its physical and mechanical behavior. The silica content in RAP is considerably higher than that of aluminium oxide, sulfur trioxide, and potassium oxide. Silica enhances pavement strength and durability by forming a robust cementitious matrix, as supported by the findings of Zhang and Liu (2019), who highlighted silica's role in improving the load-bearing capacity of recycled asphalt. Aluminium oxide increases hardness and wear resistance, improving durability under heavy traffic. Conversely, sulfur trioxide can be harmful as it may form expansive compounds like gypsum or ettringite, leading to cracking and structural degradation Potassium oxide, beneficial in small quantities for regulating cement setting time, can cause alkali-silica reaction when present in excess, resulting in severe cracking and pavement deterioration. The research by Raguraman Vaithiyasubramanian et al. (2025) emphasizes the importance of controlling potassium oxide levels to mitigate alkali-silica reaction risks and maintain pavement integrity. Balancing these components is vital for maintaining pavement longevity and reliability. Figure 2 , 3 , 4 depicts the XRF curve for Percentage Variation in concentration vs compound of RAP material The results of the XRF analysis reveal that SiO₂ (silicon dioxide) predominates in percentage composition, followed by Al₂O₃ (aluminum oxide) and CaO (calcium oxide), while Fe₂O₃ (iron oxide) has the highest concentration in ppm in the trace elements. The elemental composition influences the mechanical and durability characteristics of the material substantially; thus, it can be applied to engineering and construction uses. The existence of SiO₂ helps to add strength and durability by engaging in pozzolanic reactions with calcium hydroxide Ca(OH)2, forming more calcium silicate hydrate (C-S-H) gel, strengthening the binding characteristics of the material SiO₂ + Ca(OH) 2 →C-S-H (gel) The Al₂O₃ present may react with sulfates and calcium hydroxide in cementitious materials to form calcium aluminate hydrates (CAH), enhancing durability Al 2 ​O 3 ​+Ca(OH) 2 ​+H2​O→CAH Moreover, high levels of Fe₂O₃ indicate the material's ability to offer enhanced resistance to degradation within the environment, as the material is able to react with calcium substances, which form ferrite phases to ensure material stability Fe 2 ​O 3 ​+CaO→C-F (Calcium Ferrite) The availability of CaO shows scope for hydration reactions, which play a role in setting and hardening CaO + H 2​ O→Ca(OH )2 ​ Generally, the XRF analysis indicates that the material possesses high pozzolanic activity, high durability, and is appropriate for cementitious and pavement use, based on the chemical reactions between silica, alumina, iron oxides, and calcium compounds. 3.1.6 Fourier Transform Infrared (FTIR) analysis Fourier Transform Infrared (FTIR) spectroscopy is an important analytical technique to evaluate the chemical content and aging impact in Reclaimed Asphalt Pavement (RAP) binders. It detects oxidation indicators like carbonyl (C = O) at ~ 1700 cm⁻¹, sulfoxide (S = O) at ~ 1030 cm⁻¹, and hydroxyl (-OH) at ~ 3400 cm⁻¹, which are signs of binder aging as a result of long-term exposure to heat, oxygen, UV radiation, and water. The height of such peaks in the FTIR spectrum assists in measuring the level of binder hardening and the possibility of RAP reuse in fresh asphalt mix. FTIR also assesses the efficiency of mixing aged RAP binder with fresh binder by examining their spectra. A large gap between the mixed and new binder spectra shows low integration, calling for the use of rejuvenators to enhance compatibility. Carbonyl index (CI) and sulfoxide index (SI) measure the changes in oxidation for optimal RAP content in long-term and lasting asphalt mixtures. The FTIR analysis methodology starts from sampling and drying at temperatures less than 60°C for moisture removal without changing the chemical nature of the binder. The aged binder is next recovered from solvents such as trichloroethylene (TCE), toluene, or ethanol using Soxhlet extraction, centrifugation, or reflux techniques. Following extraction, fine particles are eliminated through filtration, and the solvent is driven off by rotary evaporation or vacuum drying under temperatures not exceeding 110°C to avoid thermal degradation. The binder recovered is examined either by the potassium bromide (KBr) pellet method, in which a translucent pellet is formed for transmission mode analysis, or by the Attenuated Total Reflectance (ATR) method, in which the sample is placed directly on the ATR crystal for ready, non-destructive examination. FTIR spectroscopic analysis is performed on a SHIMADZU IRAffinity-1S FTIR Spectrophotometer equipped with a MIRacle10 Single Reflectance ATR accessory. The spectra are captured at a resolution of 4 cm⁻¹ with 25 scans between 400–4000 cm⁻¹, which gives thorough information regarding the chemical composition and aging behavior of RAP binders. FTIR is a crucial technique for sustainable asphalt pavement management as it facilitates efficient binder rejuvenation and maximum RAP usage in new mixtures. The provided image is an FTIR (Fourier Transform Infrared) spectrum, recorded using a SHIMADZU IRAffinity-1S spectrophotometer, from the Department of Chemistry at Bannari Amman Institute of Technology. The sample code is labeled "OLDROCK," suggesting that the material analyzed is an aged or weathered rock sample. The spectrum plots transmittance (%T) against wavenumber (cm⁻¹), spanning from 4000 cm⁻¹ to 400 cm⁻¹, which is the typical mid-infrared range for FTIR analysis. Key absorption peaks are observed at specific wavenumbers, indicating the presence of various functional groups in the sample. Significant peaks include a broad absorption band around 3741.90 cm⁻¹ and 3936.71 cm⁻¹, which are characteristic of hydroxyl (-OH) stretching vibrations, suggesting the presence of water molecules or hydroxyl-containing minerals. The peaks at 2921.16 cm⁻¹ and 2357.01 cm⁻¹ could be attributed to C-H stretching vibrations, commonly found in organic compounds, or CO₂ asymmetric stretching, which is often present in carbonate minerals or atmospheric interference. The region around 561.29 cm⁻¹, 509.21 cm⁻¹, 483.71 cm⁻¹, and 430.31 cm⁻¹ typically corresponds to metal-oxygen stretching vibrations, indicative of silicates or other metal-containing minerals. The data from this FTIR spectrum provides valuable insight into the chemical composition of the "OLDROCK" sample, aiding in the identification of minerals, the presence of organic matter, or possible environmental effects such as weathering or contamination. By analysing the characteristic absorption bands, researchers can determine the sample’s mineralogical and chemical properties, making it useful for geological, environmental, and material science applications. Further comparison with standard FTIR spectra databases can help refine the interpretation of the observed peaks and confirm the presence of specific compounds. The FTIR (Fourier Transform Infrared) spectral analysis of sample NEWROCK, as carried out at 14:18:52 with a Shimadzu FTIR spectrometer in the Department of Chemistry, Bannari Amman Institute of Technology, indicates the presence of functional groups in the sample through characteristic absorption bands pointing towards the occurrence of different molecular vibrations. A wide peak at 3745.76 cm⁻¹ indicates the presence of hydroxyl (-OH) groups, which are often present in alcohols or water molecules. The peak at 2922.16 cm⁻¹ is due to C-H stretching, which is indicative of aliphatic hydrocarbons. A sharp absorption at 2360.87 cm⁻¹ may be due to atmospheric CO₂. Also, a strong absorption at 1654.28 cm⁻¹ is due to the C = O stretching, which is generally found in ketones, aldehydes, or carboxyl functional groups. The band at 1546.91 cm⁻¹ indicates the amide (-NH) groups, and the 1463.97 cm⁻¹ band indicates C-H bending vibrations. A sharp band at 1041.56 cm⁻¹ indicates the C-O stretching characteristic of alcohols or ethers. Bands in the fingerprint region at 586.36 cm⁻¹, 553.57 cm⁻¹, 509.21 cm⁻¹, and 462.92 cm⁻¹ are indicative of the presence of metal-oxygen bonds, which could point towards the presence of inorganic material. The general spectral analysis indicates the presence of hydroxyl, carbonyl, alkane, and potential inorganic functional groups in the sample. More detailed analysis involving methods like X-ray diffraction (XRD) or scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) would be useful for a clearer idea of the sample composition. 4. Effect of RAP on Pavement characteristics 4.1. Impact test The purpose of this test is to measure the resistance of the material to impact load (impact) and to determine the impact strength. Impact testing is a type of pavement quality test used to determine the suitability of aggregates for pavement construction. In general, RAP has lower impact than virgin asphalt. This decrease in strength is due to the properties of RAP, such as hardness, longer life, and the ability of bones to deteriorate over time. Kim et al. ( 2019 ) and Lee and Kim (2018) added that RAP materials will become less flexible due to aging and environmental exposure, which may cause the adhesive to harden and increase its brittleness, thus affecting its use in high-performance applications. West et al. ( 2018 ) discussed that mixing RAP with VA can increase the overall durability and impact of the mixture. This test performs impact tests on five different types of old and new RAP to determine their impact strength. The adverse impact of all composites is measured by testing tests such as the Charpy impact test apparatus described in IS 1757. To determine the impact value of RAP and VA aggregates of the previously selected combination, sizes 10 mm and 2.36 mm. This method allows reliable classification of aggregates according to IS 2386 Part 4 (1963). To obtain consistent results, composite samples were oven dried at 108°C for four hours, a process reminiscent of the work done by Tang et al. ( 2019 ) on moisture in measuring power. Samples were crushed into 10mm × 12.5 mm fines were sieved through 2.36 mm IS sieve before testing. RAP is usually obtained from old asphalt exposed to weathering, traffic and the environment due to the degradation of asphalt binder, which becomes brittle over time and reduces its impact strength. This behavior has been discussed by Kringos and Scarpas ( 2018 ), who mentioned the aging process of RAP to reduce its sealing flexibility and increase its brittleness. Improve its properties, including impact strength. According to the Asphalt Association (2019) guidelines, additives such as rejuvenators, polymers and other modifiers can improve the flexibility and performance of old asphalt binders. By adjusting the composition of asphalt mixture containing RAP, impact strength can be optimized for different applications, as suggested by Kim et al. ( 2019 ), supporting the work of RAP in solving sustainable development problems. The findings from Fig. 7 show that the addition of VA to RAP increases the Aggregate Impact Value (AIV), which enhances aggregate toughness and durability according to IS 2386 (Part IV): 1963, which indicates that lower AIV values reflect better impact resistance. For 100% RAP, AIV is 17% for OLD RAP and 16.64% for New RAP, reflecting comparatively poor toughness. With the addition of VA, however, the AIV reduces gradually, showing enhanced impact resistance. The best proportion is at 50% RAP + 50% VA, where the AIV is 12.33%, indicating a good mix composition that increases durability. Beyond this point, at 25% RAP + 75% VA, a mild rise in AIV is seen, perhaps the result of mixing variability, so an overloading VA content would not necessarily produce further gains. This underlines the need for a proper balance between RAP and VA by having an ideal RAP-to-VA ratio to attain strength as well as performance. 4.2. Crushing test Aggregate crushing strength serves as a critical indicator of an aggregate's resistance to fracture under a progressively applied compressive load, particularly relevant to evaluating material performance in pavement construction. Kandhal and Mallick ( 2001 ) emphasize the correlation between aggregate strength and pavement durability. Reclaimed asphalt pavement (RAP) exhibits variations in crushing strength due to factors such as its source, recycling methods, and the presence of contaminants or additives. West et al. ( 2018 ) highlight that binder aging, oxidation, and aggregate degradation during RAP's service life generally contribute to its lower crushing strength compared to VA. Notably, a total crushing strength exceeding 30 may indicate anomalies or deviations from expected aggregate behavior, as outlined in ASTM D6931 (2007). Refer Fig. 8 Experimental results demonstrated that all trial proportions of RAP and VA met the strength requirements specified in IS 2386 Part – 4 (1963). Specifically, mixtures with 50% RAP + 50% VA and 25% RAP + 75% VA exhibited crushing strengths comparable to VA. This observation aligns with findings by Lee and Kim (2017), who reported that blending RAP and VA in optimal proportions enhances interlocking and stability, yielding crushing values similar to VA. The angularity of RAP particles, shaped by crushing and milling processes, fosters improved interlocking in blends with VA, thereby enhancing crushing strength [76]. Studies by Kringos and Scarpas ( 2018 ), suggest that older RAP can meet structural requirements when appropriately processed and incorporated into mix designs. The chart 8 illustrates that the addition of more Virgin Aggregate (VA) with Reclaimed Asphalt Pavement (RAP) enhances the Aggregate Crushing Value (ACV), which means greater strength. At 100% RAP, the greater ACV (~ 16%) implies less durable aggregate due to the oxidation of aged binder, causing the asphalt to become brittle and susceptible to crushing. With the addition of VA, ACV reduces, and the best mix is 50% RAP + 50% VA, where the addition of fresh aggregate enhances interparticle bonding and load resistance. At 25% RAP + 75% VA, an increase in ACV might be attributed to blending irregularities, decreased bitumen adhesion, or microstructural differences in aggregate composition. The trend indicates the importance of balanced RAP-VA ratios to achieve optimal mechanical performance while ensuring sustainability. 4.3. Compaction tests Compaction tests for Recycled Asphalt Pavement (RAP) are critical to determining its fitness for use in pavement construction. Compaction tests assist in the determination of RAP's density and void content, both of which play an important role in determining the structural strength, durability, and overall performance of the pavement. For the Standard Proctor Test (IS 2720 Part 7), a mold with a capacity of 1000 cm³ is used, having an internal diameter of 100 mm and a height of 127.3 mm. In this test, a hammer weighing 2.6 kg is dropped from a height of 310 mm to compact the material. For the Modified Proctor Test (IS 2720 Part 8), a larger mold with a capacity of 2250 cm³ is used, with an internal diameter of 150 mm and a height of 127.3 mm. This test uses a heavier hammer weighing 4.89 kg, which is dropped from a height of 450 mm to achieve higher compaction energy. In this research work, various blends of RAP and virgin aggregates (VA) were prepared in accordance with previously determined mix proportions. In order to improve the mechanical properties of the mixtures, stabilizing additives like cement, fly ash, and ground granulated blast furnace slag (GGBS) were added at percentages ranging from 3%, 5%, and 7%. These stabilizers have been commonly known to enhance the strength and stability of asphalt mixtures. For accurate and uniform results, both VA and RAP underwent the process of drying to remove any residual moisture for 48 hours prior to testing. Remove large aggregates (> 19 mm) to ensure consistency in compactionIn this study, various blends of RAP and VA were prepared based on previously selected proportions. Additives such as cement, fly ash, and GGBS were incorporated in varying percentages of 3%, 5%, and 7%. The use of these additives has been shown to enhance the mechanical properties of asphalt mixtures [43]. To ensure accurate results, both the VA and RAP were dried for 48 hours to eliminate moisture content. The specimens were then compacted using a hammer with a free fall distance of 457 mm and a weight of 4.5 kg. The results, depicted in Figs. 9 – 15 , indicate a slight increase in density, while the OMC remained relatively consistent across the various blends. This consistency suggests that while the addition of materials may enhance the density of the mixtures, the moisture content at which optimal compaction occurs is stable. Such findings align with previous research indicating that the properties of asphalt mixtures can be significantly improved through careful optimization of mix designs (Sireesh 2016). Table 5 Compaction results of different mixes of RAP additives ADDITIVES % 100 RAP% 75%RAP 25%VA 50%RAP 50%VA 25%RAP 75%VA 100 VA% OMC% MDDGM/CC OMC% MDDGM/CC OMC% MDDGM/CC OMC% MDDGM/CC OMC% MDDGM/CC 3% Cement 9.9 1.48 9.9 1.50 9.9 2.17 9.9 2 9.9 1.9 5% Cement 9.7 1.45 9.7 1.75 9.7 2.2 9.7 2 9.7 1.9 7% Cement 9.7 1.69 9.7 1.85 9.7 2.24 9.7 2.2 9.7 2.22 3% FA 9.9 1.45 9.9 1.48 9.9 1.89 9.9 1.95 9.9 1.9 5% FA 9.8 1.45 9.8 1.55 9.8 1.95 9.8 1.75 9.8 1.95 7% FA 9.7 1.65 9.7 1.65 9.7 2.35 9.7 1.7 9.7 2.1 3% GGBS 9.9 1.25 9.9 1.45 9.9 1.95 9.9 1.40 9.9 1.45 5% GGBS 9.8 1.35 9.8 1.41 9.8 1.85 9.8 1.48 9.8 1.40 7% GGBS 9.7 1.40 9.7 1.48 9.7 1.9 9.7 1.55 9.7 1.50 The observed increase in maximum dry density (MDD) and optimum moisture content (OMC) in the 50% virgin aggregate (VA) blend with a 7% cement additive is attributed to the fundamental principles of soil stabilization, cement hydration, and particle packing. Cement acts as a binding agent, promoting hydration reactions that produce calcium silicate hydrates (C-S-H) and calcium aluminate hydrates (C-A-H), which enhance inter-particle bonding and reduce void spaces, leading to a denser and more compact structure. Cement addition also enhances RAP-VA granular interlock, improving compaction efficiency and mechanical stability. In addition, the optimum moisture content (OMC) of 9% allows for appropriate hydration to provide adequate lubrication among the particles during compaction and avoid unnecessary porosity. This enhanced densification increases load-bearing capacity, deformation resistance, and cracking resistance, rendering the RAP-cement mixture an ideal choice for pavement base and subbase. Moreover, cement stabilization with reduced permeability stops water intrusion, hence avoiding moisture-induced distress and ensuring longer pavement life. These reasons account for the enhanced mechanical properties, longevity, and sustainability of RAP-cement mixtures, which render them a successful option for road construction while fostering eco-friendly infrastructure development. Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) of Virgin Aggregate (VA) mixed with Reclaimed Asphalt Pavement (RAP) are the important parameters for compaction properties, and incorporation of Fly Ash as a stabilizer has an important bearing on these properties. Figures 12, 13 , and 14 show the changes in MDD and OMC for varying RAP-VA mix proportions with 3%, 5%, and 7% Fly Ash, respectively. In general, when the RAP content is increased in the blend, MDD will decrease as a result of the lower unit weight of RAP than that of VA. Moreover, as the Fly Ash content increases from 3–7%, MDD has a trend to decrease in some instances because of the reduced specific gravity and finer particle size of Fly Ash, which can influence the efficiency of compaction. Yet, there is a point of optimal Fly Ash content where its binding capability adds value without causing much density loss From the Fig. 15 – 17 shows the change in dry density with optimum moisture content (OMC) for various RAP-VA ratios stabilized with Ground Granulated Blast Furnace Slag (GGBS) at 3%, 5%, and 7%. The findings show that with increasing GGBS content, the dry density increases considerably at an optimal RAP-VA ratio. Maximum density is found at 50% RAP + 50% VA, indicating good particle packing and pozzolanic reaction because of the availability of CaO, SiO₂, and Al₂O₃ in GGBS, which provides cementitious bonding. But beyond this proportion, at 75% VA, the density is reduced, probably because of improper blending of RAP and low cohesive properties. The OMC variation is due to the water absorption potential of RAP, where higher RAP content holds water, slowing down hydration reactions. The 5% and 7% GGBS peak densities show higher pozzolanic activity, but more than 7% GGBS can cause unreacted particles that decrease compactness. The results highlight the need for a balanced RAP-VA ratio with the optimal GGBS dose to ensure better strength and durability in pavement material. Referring to the Figs. 9 to 17 , it is evident that the 50% virgin aggregates (VA) blend exhibited a higher maximum dry density (MDD) with an optimum moisture content (OMC) of 9% when combined with a 7% additive of cement. This finding aligns with previous studies indicating that the addition of cement improves the density and stability of asphalt mixtures. Compaction tests demonstrate that mixing RAP with cement enhances stability and reduces permeability, making it highly suitable for base and subbase layers in pavement construction. The optimized blend typically achieves a higher dry density and improved moisture retention, leading to stronger and more durable pavement layers. Additionally, incorporating cement significantly enhances the mechanical properties and load-bearing capacity of RAP, which in turn improves resistance to deformation and cracking. This is particularly important in ensuring the longevity of pavement structures, as noted by Rao et al. (2015). These benefits contribute to a longer pavement lifespan and reduced maintenance costs, establishing RAP-cement blends as a sustainable and efficient choice for road construction (Kandhal and mallick 2001 ]. By optimizing the mix design and carefully selecting additives, the performance of RAP in pavement applications can be significantly improved, aligning with the goals of sustainable infrastructure development (Taha 2002). 4. 4. Unconfined compressive strength (UCS) The UCS test is used to determine the compressive strength of materials utilized in pavement. UCS is one of the most important mechanical properties of aggregates and is widely used in projects to evaluate the stability of pavements against loading [66]. Many authors have relied on the UCS test to determine the shear strength of pavements, with studies indicating that UCS is crucial for assessing the load-bearing capacity of pavement materials (Saride et al 2016). Data show that UCS can be improved by mixing cement, fly ash, and stabilizers such as GGBS. Cementitious materials like cement react with the fine particles of asphalt binder and aggregates present in RAP, facilitating pozzolanic reactions that form additional cementitious compounds, thereby enhancing the strength and durability of the blend. RAP contains fine particles that can act as fillers within the cement matrix, reducing the overall porosity of the material and enhancing its strength by filling the voids between cement grains The addition of cement improves the resistance of the pavement to rutting, which is the permanent deformation caused by repeated traffic loading. Cement helps to stiffen the RAP mixture, thereby mitigating rutting and improving the long-term performance of the pavement, as noted by (Dong Q, Huang B 2014 ). The addition of fly ash significantly increased the UCS of 100% RAP mixed with fly ash blends(Saride et al 2015 ). The incorporation of fly ash alongside RAP assists in filling the voids between larger aggregates, reducing porosity and increasing the density of the pavement. This filler effect contributes to improved mechanical properties, including increased UCS, as emphasized by Jayakody et al. (2017). Since VA is better integrated with RAP, the UCS value increases as VA content increases [74]. Samples of 100 mm in length and 200 mm in height were prepared from each combination. To determine the MDD and OMC, casting samples were tested according to IRC Specification: 37-2012, which recommends a minimum pressure of 4.5 MPa at 28 days of curing. Figures 18 , 19 , and 20 show the compressive strength of RAP + VA with the addition of different proportions of cement, fly ash, and GGBS. The UCS results revealed that 50% RAP + 50% VA mixes showed higher strength than 100% RAP. In general, RAP exhibits a lower UCS compared to conventional asphalt mixtures due to the aging of the asphalt binder, and it may contain moisture and contaminants in the recycled material (Vidal 2013). However, advances in technology and the inclusion of additional materials can enhance the strength of RAP, enabling its effective use in pavement applications. Consequently, RAP can be blended with additives like cement, fly ash, and GGBS. The adopted mix proportions and the strength evaluations of these mixes are reported in Table 5 to 7 . Table 5 Different proportions of RAP with VA for UCS test ADDITIVES % 100 RAP% UCS (N/ MM2) 75%RAP 25%VA UCS (N/ MM2) 50%RAP 50%VA UCS (N/ MM2) 25%RAP 75%VA UCS (N/ MM2) 100 VA% UCS (N/ MM2) 3% Cement 3.50 3.03 4.78 3.98 4.35 5% Cement 3.57 2.87 4.78 4.08 4.50 7% Cement 3.66 3.12 4.98 4.20 4. 85 3% FA 3.12 2.61 4.20 4.14 4.25 5% FA 3.18 2.71 4.30 4.17 4.35 7% FA 3.50 3.03 4.94 4.20 4.66 3% GGBS 3.18 3.12 4.14 3.89 3.66 5% GGBS 3.20 3.32 4.54 4.14 3.82 7% GGBS 3.27 3.38 4.78 4.30 3.95 The Table 5 presents the Unconfined Compressive Strength (UCS) values in N/mm² for different compositions of Reclaimed Asphalt Pavement (RAP) and Virgin Aggregate (VA) mixtures, stabilized with varying percentages of Cement, Fly Ash (FA), and Ground Granulated Blast Furnace Slag (GGBS). The tests reveal that the strength of the mixes depends on the stabilizer type and percent, as well as the percentage of RAP and VA used in the mix. Cement-stabilized blends typically have the highest UCS values among various RAP-VA compositions, with cement content increasing strength. The highest UCS of 4.98 N/mm² is attained by the 50% RAP – 50% VA mix with 7% cement among all mixes, indicating a balanced mixture between RAP and VA when cement is employed as a stabilizer. The UCS values for 100% RAP are lower than those for mixes with VA, indicating the necessity of mixing RAP with virgin aggregates to achieve structural strength. Fly Ash-stabilized mixtures exhibit comparatively lower UCS values than cement-stabilized ones. But a rising proportion of FA leads to an improvement in strength, though not very high. The maximum UCS (4.94 N/mm²) for FA-stabilized mixtures is seen in the 50% RAP – 50% VA mixture with 7% FA, which means FA can prove to be a good stabilizer when utilized in suitable proportions. GGBS-stabilized mixtures typically have lower UCS values than cement and FA. The strength of GGBS-stabilized mixtures increases with increasing VA content, and the maximum UCS of 4.78 N/mm² was achieved for the 50% RAP – 50% VA mix containing 7% GGBS. While GGBS enhances strength, its effect seems less pronounced than that of cement. In general, the results indicate that the addition of a balanced ratio of RAP and VA improves the mechanical performance of the mixture, with the 50% RAP – 50% VA mixture producing the highest UCS in all the stabilizers. Cement is found to be the best stabilizer, followed by FA and GGBS. The findings emphasize the possibility of utilizing RAP with suitable stabilizers to obtain a sustainable and structurally adequate pavement material. 4.5 Indirect tensile strength (Moisture Sensitivity test) Indirect Tensile Strength (ITS) is a crucial test for evaluating the tensile strength and moisture susceptibility of bituminous mixes, including Reclaimed Asphalt Pavement (RAP)-based mixes. It helps in assessing cracking resistance under repeated traffic loads. The Indirect Tensile Strength (ITS) of Reclaimed Asphalt Pavement (RAP) can be significantly enhanced through the incorporation of stabilizing agents such as cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) by ASTM D6931 or AASHTO T 283. Studies by Taha et al. (2002) and Modarres & Ayar (2014) have shown that cement improves the mechanical properties of RAP by acting as a hydraulic binder, increasing stiffness and strength. Similarly, research by Kim et al. ( 2018 ) highlights the role of fly ash, a pozzolanic material, in long-term strength gain, as it reacts with available lime to form additional binding compounds, thereby improving cohesion. The combined effect of these additives results in an increased ITS, as observed in the studies by Mohammadinia et al. (2017), indicating better resistance to tensile cracking and improved load-bearing capacity. However, as noted by Wen et al. (2013), the effectiveness of these stabilizers depends on several factors, including the percentage of additives, curing period, RAP gradation, and moisture content. Proper optimization of these parameters ensures a balance between flexibility and strength, making RAP a viable and sustainable material for pavement rehabilitation and construction. Each of these RAP:VA blends was further stabilized with cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) at varying percentages of 3%, 5%, and 7% by weight of the total mixture. The IDT strength test was used to determine tensile strength and strain of the mixture specimens compacted to 4 ± 1% air voids. Cylindrical specimens with 100 mm in diameter and 63.5mm in height were monotonically loaded to failure along the vertical diametric axis at the constant rate of 76.2 mm/min. Table 6 Indirect tensile strength of RAP + VA mixes with various proportions Additives % 100 RAP% ITS (N/ mm 2 ) 75%RAP 25%VA ITS (N/ mm 2 ) 50%RAP 50%VA ITS (N/ mm 2 ) 25%RAP 75%VA ITS (N/ mm 2 ) 100 VA% ITS (N/ mm 2 ) 3% Cement 1.35 1.56 1.75 1.75 2.05 5% Cement 1.55 1.76 1.85 1.95 2.15 7% Cement 2.45 2.56 2.75 2.75 2.85 3% FA 1.25 1.36 1.55 1.78 2.05 5% FA 1.35 1.56 1.75 1.75 2.15 7% FA 1.75 1.86 1.95 1.97 2.25 3% GGBS 1.15 1.26 1.45 1.65 1.65 5% GGBS 1.27 1.36 1.45 1.55 2.05 7% GGBS 1.35 1.46 1.55 1.78 2.15 Refer table: 6 Indirect Tensile Strength (ITS) of Reclaimed Asphalt Pavement (RAP) and Virgin Aggregate (VA) blends largely depends on the type and quantity of additives used for stabilization. The values given indicate differences in ITS values among different RAP-VA mixes stabilized with different percentages of Cement, Fly Ash (FA), and Ground Granulated Blast Furnace Slag (GGBS). With the increasing proportion of VA in the blend, ITS values tend to increase, reflecting better strength resulting from the enhanced interlocking and compaction behavior of VA over RAP Refer Fig. 21 to 23 among the stabilizers, cement has the highest ITS values for all RAP-VA ratios, with a significant increase as the cement content increases from 3–7%. At 7% cement, the maximum ITS value of 2.85 N/mm² is recorded for 100% VA, and even the mixtures with higher RAP content (100% RAP and 75% RAP-25% VA) exhibit significant tensile strength improvements. This is due to the fact that cement has better binding qualities, which increase the cohesion and structural strength of the mix. Fly Ash also enhances ITS, but its effect is comparatively moderate in nature relative to cement. At 7% FA, ITS values vary from 1.75 N/mm² for 100% RAP to 2.25 N/mm² for 100% VA, indicating that FA helps in strength gain but does not offer as much binding capacity as cement. Nevertheless, its capacity to enhance workability and minimize moisture susceptibility makes it a good substitute for RAP stabilization. GGBS follows a similar pattern but with lower ITS values than cement and FA. ITS values are higher with greater VA content, but even at 7% GGBS, the maximum strength achieved is 2.15 N/mm² for 100% VA. This suggests that although GGBS is strength-enhancing, its stabilizing effect is relatively lower than cement and FA in tensile resistance. In general, the choice of stabilizers is a function of strength requirements and material availability. Cement yields the highest strength increments and is the first choice for applications requiring high durability. Fly Ash gives balanced improvement in strength and workability, while GGBS, while less efficient in raising ITS, remains a suitable stabilizer in RAP-VA mixtures. These results emphasize the need to choose the right additives in accordance with project needs to maximize pavement performance. 4.5. California bearing ratio The California Bearing Ratio (CBR) test is crucial for predicting the durability and mechanical properties of compacted materials. It serves as a key specification for defining the bearing capacity of pavement under traffic loading, ultimately influencing pavement thickness. Laboratory studies consistently demonstrate that CBR values increase with a higher percentage of VA) while decreasing with an increased presence of RAP in the mix [75]. To enhance the strength of the pavement base layer, additives such as Portland cement (PC), fly ash, and ground granulated blast furnace slag (GGBS) can be effectively incorporated with RAP. Testing the load-bearing capacity of 100% RAP combined with 1%, 2%, and 3% cement revealed that a mix of 50% RAP and 50% limerock-based asphalt emulsion achieved CBR values exceeding 100 [15]. The combination of RAP with recycled coarse aggregates (RCA) has also shown promising results, with studies indicating that RCA enhances load-bearing capacity and durability(Seferoǧlu 2018). According to recommendations from the Queensland Department of Transport and Highways (QDTMR), a high RAP content of 20% is feasible for pavement layers. Moreover, crushed clay bricks combined with RCA have demonstrated sufficient strength for use as unbound subbase material (Poon 2006 ). The improvement of mechanical properties in RCA and limestone aggregate (LSA) enhances their suitability for road subbases or bases. CBR values tend to increase with a higher RCA content and a lower RAP percentage, indicating RCA's superior quality compared to RAP. Optimal CBR values of approximately 78% have been achieved with a mix containing a maximum of 15% RAP. However, higher RAP content results in decreased CBR values, primarily due to the bitumen-coated aggregates sliding over each other under load. The best pavement performance is generally observed with a 50/50 mixture of RAP and RCA [10]. CBR tests conducted on samples with varying RAP and VA contents have shown that 100% RAP does not provide acceptable base course quality. As RAP content increases, CBR values fall below acceptable levels, leading to a recommendation of limiting RAP to 50% when combined with 50% VA. The reduced strength is attributed to the lower viscosity of the bituminous binder, which causes increased deformation under summer conditions and traffic loads. Specifically, when RAP content rises from 0–25% and from 50–75%, CBR results decrease by 50–75% and 75–100%, respectively. Notably, when RAP is blended with an optimum of 7% cement, higher CBR values are observed. Furthermore, cement-treated RAP combined with VA outperforms mixes treated with fly ash and GGBS, reinforcing the importance of optimizing blend ratios for enhanced pavement performance. From the Fig. 24–26 clearly shows that Variation in CBR with different blends of RAP with varying percentage of cement, fly ash and GGBS. From the test result a balanced mix—typically a 50/50 ratio of Reclaimed Asphalt Pavement (RAP) optimizes California Bearing Ratio (CBR), often exceeding 100, demonstrating sufficient durability and load-bearing capacity. A recent study by Mishra et al. ( 2021 ) has confirmed that this balanced RAP ratio provides an ideal compromise between sustainability and mechanical performance. Cement-treated RAP and virgin aggregate (VA) blends exhibit the highest CBR values, outperforming those treated with fly ash or Ground Granulated Blast Furnace Slag (GGBS), highlighting the need for optimized blend ratios to enhance pavement performance. For practical applications, limiting RAP to around 50% and incorporating strength-enhancing additives like cement offers a promising approach to maintaining pavement integrity under traffic loading (Deng 2021). When cement is introduced into a RAP mix, a pozzolanic reaction occurs between the cement and the finer particles in the RAP. Recent findings by Zhao and Zhang (2012) indicate that cement hydration products improve cohesion in RAP mixes. Cement hydrates react with the bituminous coating on RAP aggregates, partially stripping the bitumen and forming a more cohesive matrix, resulting in improved bonding and a stiffer, more durable layer. This process enhances the structural integrity of the RAP mix by reducing the inherent weakness associated with bitumen-coated surfaces that can otherwise slip under load. The chemical bonds formed between the cement and RAP particles offset the otherwise low CBR values typically seen in high RAP content mixtures. While RAP is a cost-effective and sustainable material, limiting its percentage in a pavement mix to around 50% is crucial to maintaining optimal performance. As demonstrated by (Wang et al. 2023 ), high RAP content can lead to an excess of bituminous material, which may reduce friction between particles and compromise strength under load. Refer Fig. 19 to 21 a balanced 50/50 RAP-VA blend maximizes load-bearing capacity while preserving pavement integrity, as the fresh aggregates provide structural support that counteracts RAP’s reduced frictional resistance. This balance also helps to avoid excessive brittleness or susceptibility to fatigue, which is more likely when RAP content exceeds 50%, especially under high traffic loads. The results of CBR revealed that, for all additives, 50% RAP with 50% VA blends have given higher CBR, with increase in RAP proportion, CBR decreases due to reduced stiffness and gradation change in the mix. 4.6. Marshall stability test The Marshall Stability test is a crucial laboratory procedure used to assess the performance and durability of asphalt mixtures, including those incorporating reclaimed materials. This test measures an asphalt mixture's resistance to deformation and failure under standardized conditions, ensuring that the mix meets specified performance and durability standards (ASTM D1559). According to Prajnas and Ilyas Anjum (2014), the test evaluates both stability and flowability, making it valuable for assessing RAP-based mixes. Several studies have indicated that the incorporation of cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) into Reclaimed Asphalt Pavement (RAP) significantly improves both the mechanical properties and the durability of RAP mixtures. As noted by Zhao et al. ( 2020 ), cement and fly ash increase stability and stiffness through enhanced binder-aggregate bonding, while GGBS provides additional strength and moisture resistance. The synergy of these additives addresses the aged binder's rigidity in RAP, resulting in a more workable and resilient mix (Zhao et al 2012 ). Research highlights that optimal combinations of RAP with cement, fly ash, and GGBS achieve stability values comparable to or exceeding traditional asphalt mixtures, making them suitable for high-traffic applications. This approach supports sustainable pavement design by effectively recycling materials while preserving structural integrity and longevity. The Marshall Stability Test is primarily utilized to measure the deformation properties and strength of asphalt mixtures but is not a stiffness analysis in direct terms. Rather, it determines the stability and flow, which indirectly reflect the mix's resistance to cracking and rutting. Whereas the test gives insight into the total load-bearing capacity, it does not uniquely measure stiffness as tests such as the Dynamic Modulus or Indirect Tensile Stiffness Modulus (ITSM) Test are better applicable to stiffness analysis. Increased Marshall stability value can, however, be related to higher mix stiffness, but this is not enough for complete stiffness characterization, particularly for RAP mixes. Table 7 Nomenclature followed for different proportions of RAP with VA for Marshall stability test ADDITIVES % 100 RAP% 75%RAP 25%VA 50%RAP 50%VA 25%RAP 75%VA 100 VA% Stability (kN) Flow (mm) Stability (kN) Flow(mm) Stability (kN) Flow (mm) Stability(kN) Flow (mm) Stability (kN) Flow (mm) 3% Cement 12.2 1.56 12.55 1.66 13.25 2.35 13 2.15 13.15 2.05 5% Cement 13.45 1.68 14.55 1.78 13.45 2.50 13.05 2.20 13.15 2.10 7% Cement 15.55 1.77 16.57 1.87 17.55 3.35 17.5 3.05 17.25 2.95 3% FA 13.32 1.45 13.35 1.35 14.01 2.25 14.01 2.15 14.01 2.25 5% FA 14.45 1.67 14.55 1.57 15.09 2.56 15.79 2.52 15..02 2.56 7% FA 15.67 1.98 15.58 1.88 15.67 2.76 15.89 2.34 15.76 2.76 3% GGBS 11.56 1.35 12.01 1.45 11.95 2.25 11.86 2.15 11.85 2.25 5% GGBS 12.68 1.45 12.05 1.55 12.95 2.46 13.01 2.36 12.85 2.46 7% GGBS 14.56 1.67 13.05 1.79 15.09 2.65 15.56 2.45 15.09 2.65 A mixture of 50% Reclaimed Asphalt Pavement (RAP) and 50% virgin aggregate (VA) stabilized with 7% cement gains strength due to enhanced bonding and rigidity. Cement binds the RAP and VA particles, creating a dense, cohesive matrix that resists deformation(Ranjitham Mariyappan et al 2022 ].This reduces voids, improves load distribution, and enhances moisture resistance, resulting in greater durability. The cement also stabilizes the aged binder in RAP, contributing to stronger aggregate-binder interaction. Together, these factors provide a high-strength, long-lasting pavement mix. In the Marshall stability test, the 50% RAP and 50% VA mixture stabilized with 7% cement demonstrates high stability due to the improved bonding, rigidity, and reduced voids provided by cement. The dense, cohesive matrix enhances load-bearing capacity, distributes stresses effectively, and improves moisture resistance, leading to greater durability. The cement's stabilization of the aged RAP binder strengthens the aggregate-binder interaction, contributing to a high-strength, resilient pavement mix well-suited for long-term performance under traffic loading. 4.7 Scope of cost-benefit analysis The essential reuse of discarded waste materials for environment-friendly solutions in pavement protection, conservation, and reconstruction has been extensively appraised in recent years (Li et al 2021). Thousands of tons of waste are produced worldwide every year, which can be reprocessed and reused on roads, safeguarding the environment by reducing waste and saving materials (Tighe et al 2015). The analysis of low energy consumption in transportation is mainly divided into two ways: (1) reducing the cost of asphalt pavement and reducing the cost of materials(Brown 2009). In this study, various composites were produced, but HMA performance was not considered. Therefore, the main purpose of this study is to follow the second method, material cost analysis, while exploring other methods. Loading, milling, placement, and contract work are not included in the estimated cost because these activities are the same for virgin materials RAP (Recycled Asphalt Pavement) is an admirable material used in highway construction(Li et al 2021). Using RAP is a constructive strategy because recycled materials reduce the need for virgin materials, thus making road construction more sustainable. Additionally, incorporating RAP into the asphalt mixture can recover pavement performance and durability, thereby reducing maintenance and repair costs over the life of the pavement. From an environmental perspective, the use of RAP reduces the demand on natural resources and minimizes landfill waste [46]. In general, cost savings of 20–50% can be achieved using RAP compared to conventional asphalt mixtures made from virgin materials (Chen 2014). These savings result from reduced equipment costs, transportation costs, and maintenance costs over the life of the coating (Park et al 2015 ). Overall, the cost-benefit analysis of recycled asphalt pavement demonstrates its economic and environmental benefits, making it a sustainable choice for road construction and rehabilitation projects (Sharma et al 2018). The minimization of landfill waste from the utilization of Reclaimed Asphalt Pavement (RAP) is motivated by numerous factors. RAP facilitates recycling of aged asphalt, reducing enormously the quantity of construction waste to be sent to landfills. Through the application of RAP in new pavements, utilization of virgin aggregates is reduced, thus preserving nature and minimizing material extraction's adverse effects on the environment. Apart from that, reuse of RAP decreases energy usage in the production of asphalt, thus saving costs in road construction. Circular economy principles are enhanced by sustainable pavement practices, which ensure material reuse instead of disposal. Additionally, use of RAP is in line with environmental policy and regulations as well as waste management policies, and it promotes environmentally friendly construction practices. RAP is an essential tool for achieving sustainable construction methodologies in road infrastructure through minimizing dependence on virgin resources and environmental pollution. Through the use of RAP in fresh asphalt mix, the use of natural aggregates is greatly reduced, thus preserving non-renewable resources. The recycling of asphalt pavement also prevents construction and demolition waste, whereby huge amounts of material are not sent to landfill. In addition, RAP helps improve energy efficiency by reducing the demand for significant material processing and lowering emissions from asphalt production. The cost savings of RAP also help improve sustainability since it reduces material and transport costs while conserving pavement performance. Further, RAP use helps promote circular economy ideals by establishing a closed-loop process in which materials are recycled repeatedly and conform to environmental controls and green infrastructure practices. By incorporating RAP into road building, planners and engineers achieve long-term sustainability as well as enhancing the resilience and durability of transportation infrastructure. 4.8 Life Cycle Analysis (LCA) of Reclaimed Asphalt Pavement (RAP) RAP Life Cycle Analysis (LCA) evaluates its entire life cycle environmental impacts from extraction to recycling or disposal. RAP normally originates from the milling or asphalt stripping from previously laid pavements as part of resurfacing or reconstruction jobs. This method minimizes the demand for virgin raw material to a considerable extent, since it facilitates reusing the top asphalt layer and thus lessens the environmental load of virgin material extraction (Zhang et al., 2020). Through the utilization of RAP, the demand for new aggregates as well as bitumen is reduced, according to (McDaniel et al. 2011), making it a green solution for conventional construction material. After RAP is gathered, it is taken to processing plants or to building sites, and transportation effects such as fuel use and GHG emissions are factored in. The magnitude of these effects is a function of factors like distance covered and type of transport utilized (i.e., truck or train. During the processing phase, RAP is generally screened, crushed, and heated prior to being utilized in new asphalt mixtures. Even though energy is needed for such processes, research indicates that the energy consumption of RAP is much lower than that of virgin material production (Li et al., 2021). Additionally, the emissions produced during the processing of RAP are much lower than those produced in fresh asphalt production. With the use of RAP in fresh asphalt mix, it not only lowers the requirements for virgin resources but also maximizes the sustainability of pavement making through minimizing wastes and saving resources (Zhang et al., 2020). Studies conducted by Lippiatt et al. (2019) illustrate that recycling RAP can help reduce material cost as well as carbon emissions during asphalt production. At the end of its life cycle, RAP is still a useful material for future recycling in paving projects, encouraging a circular economy. As noted by Giani et al. (2020), repeated recycling of RAP through several life cycles can effectively minimize environmental effects, as well as natural resource consumption. Overall, utilization of RAP in roadwork provides a number of environmental benefits, such as minimizing waste generation, saving natural resources, and conserving energy, hence the integral part of sustainable infrastructure planning. By mitigating the dependence on virgin resources and advancing towards a circular economy, RAP is an essential component in bringing down the environmental footprint of construction. 6. CONCLUSION RAP materials exhibited coarser gradation compared to virgin aggregates (VA), affecting compaction and interlocking properties. Proper blending with VA improved particle packing, reducing voids and enhancing structural integrity. RAP mixes needed more energy to mix because of hardened binder characteristics. Mixing with VA and stabilizers enhanced workability of the mix, facilitating uniform binder and fines distribution. The 50% RAP–50% VA blend with 7% cement had the greatest Maximum Dry Density (MDD) and optimum Optimum Moisture Content (OMC) and had superior compaction as well as better structural stability and was appropriate for road base and subbase constructions. Unconfined Compressive Strength (UCS) results established that the cement-stabilized RAP-VA combinations had the best strength with an optimum UCS value of 4.98 N/mm² and greatly enhanced resistance to load over unstabilized RAP. The California Bearing Ratio (CBR) test showed that the RAP-VA mix stabilized with cement had the greatest CBR value of 108%, which represents improved load-carrying capacity for use in high-traffic pavements and environmentally friendly road construction. Indirect Tensile Strength (ITS) tests showed that tensile strength was greatly enhanced by cement stabilization with a peak ITS of 2.75 N/mm², providing enhanced crack resistance. FA-treated mixtures recorded 1.97 N/mm², and GGBS-treated mixtures recorded 1.45 N/mm², indicating the efficacy of cement as a stabilizer. Marshall Stability test upheld that the deformation resistance of cement-stabilized RAP-VA mix was superior, which registered a peak stability of 15.6 kN compared to FA-stabilized (14.8 kN) and GGBS-stabilized (14.2 kN) mixes and thus proves best suited for high-performance asphalt pavement. Analysis through X-ray Fluorescence (XRF) revealed that the major oxides present in RAP include SiO₂, Al₂O₃, CaO, and Fe₂O₃ with more silica being more beneficial towards improving aggregate durability and mechanical strength. Fourier Transform Infrared Spectroscopy (FT-IR) analysis identified oxidation markers like carbonyl (C = O) at ~ 1700 cm⁻¹, sulfoxide (S = O) at ~ 1030 cm⁻¹, and hydroxyl (-OH) at ~ 3400 cm⁻¹, validating binder aging and the need for rejuvenators to rehabilitate asphalt characteristics towards long-term pavement sustainability. Environmental and economic benefits were evident since RAP use drastically cuts virgin aggregate consumption, reduces construction costs, and facilitates sustainable pavement construction in harmony with circular economy. The study demonstrates that cement-stabilized RAP-VA mixes offer superior strength, improved durability, and greater deformation resistance, positioning them as a feasible, cost-efficient, and sustainable option for contemporary road infrastructure. RAP use lessens the reliance on virgin aggregates, decreases asphalt binder usage, and reduces construction waste, promoting sustainable and environmentally friendly practices in pavement construction. Based on the test results, when the RAP percentage exceeds 50%, the strength decreases due to limited binder availability, increased material stiffness, and insufficient blending with virgin aggregates, resulting in reduced structural integrity. 7. FUTURE STUDY Innovative approaches, such as bio-based rejuvenators and chemical additives, can enhance the flexibility and durability of RAP mixes while minimizing environmental impact. Further studies should evaluate the long-term environmental benefits of high RAP content in asphalt mixes, including reduced carbon emissions, lower energy consumption, and waste minimization. Additionally, exploring the integration of other recycled materials, such as waste plastics or industrial by-products, can enhance sustainability. The use of rejuvenators and softening agents in RAP can significantly improve binder flexibility and reduce brittleness. Research should focus on optimizing dosages and formulations to enhance resistance to moisture damage, fatigue cracking, and oxidation. The incorporation of fibers in high-RAP asphalt mixes presents a promising avenue to improve durability, stability, and cracking resistance. Future studies should explore various fiber types, such as cellulose, polymer, or steel fibers, to determine their optimum contribution to mix performance. The synergistic effects of additives, such as polymer modifiers and supplementary cementitious materials, require further investigation. These additives can enhance rutting resistance, moisture susceptibility, and overall structural integrity of RAP-based pavement layers. While laboratory studies provide valuable insights, long-term field performance evaluations are necessary to validate RAP stabilization techniques. Research should focus on real-world pavement monitoring, assessing factors like traffic load response, climate effects, and maintenance needs for high-RAP pavements. Declarations Acknowledgements The authors acknowledge the infrastructural facilities and manpower resources provided by the Bannari amman institute of technology, Sathy, Erode, Tamilnadu, India for the execution of the project work. Funding The authors did not receive any specific funding for this work. Or: No funds, grants, or other support was received for conducting this study. Author Contributions Ranjitham conducted the research and wrote the manuscript. Jeyapriya and Soundara critically reviewed and revised the content. All authors read and approved the final version of the manuscript. Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors. Consent to participate Not applicable. Consent for publish All authors give consent for the publication that the research details in the paper are to be published in this journal. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Data availability The data that guide the results of this research will be available openly. 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Wang L, Li H & Chen Y, “Mechanical performance of high RAP content mixtures in pavement base layers”, International Journal of Pavement Engineering , v.24, n.5, pp.623-631, 2023. West R, Copeland A & King G, "Asphalt Binder Aging and Its Implications on Recycled Material Usage and Performance", Transportation Research Record: Journal of the Transportation Research Board , v.2672, n.28, pp.1-9, 2018, https://doi.org/10.1177/0361198118758699. Zhao Y, Wu S, Zhang Y & Chen Z, "Investigation of the dynamic modulus of asphalt mixtures containing reclaimed asphalt pavement (RAP)", Construction and Building Materials , v.31, pp.50-56, 2012, https://doi.org/10.1016/j.conbuildmat.2011.12.075. Zhao Z, Xiao F, Amirkhanian S, “Recent applications of waste solid materials in pavement engineering”, Waste Management, v.108, pp.78–105, 2020. Zhang And Liu, "Investigation of XRD Analysis on Reclaimed Asphalt Pavement (RAP) to Understand Material Properties and Aging Effects", Construction and Building Materials , v.227, pp.1166–1176, 2019, https://doi.org/10.1016/j.conbuildmat.2019.116566. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Major Revision 02 Oct, 2025 Reviewers agreed at journal 30 Jul, 2025 Reviewers invited by journal 25 Jul, 2025 Editor assigned by journal 15 Jul, 2025 First submitted to journal 10 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6961746","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":490775602,"identity":"89cffe52-699d-463b-ba92-76da06af050a","order_by":0,"name":"ranjitham 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cement\u003c/p\u003e","description":"","filename":"floatimage21.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/38b3f7e196dbadb5db1eca1d.png"},{"id":87918028,"identity":"fcfe2adf-2468-45be-b3db-9e5e1bcbec4b","added_by":"auto","created_at":"2025-07-30 11:21:49","extension":"png","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":361140,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 22\u003c/strong\u003e: Variation in ITS with different blends of RAP with varying percentage Flyash\u003c/p\u003e","description":"","filename":"floatimage22.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/95e70e31cd48f92cdf085354.png"},{"id":87918069,"identity":"29f7bbfb-3b57-4da3-8954-7fa9fdd299ba","added_by":"auto","created_at":"2025-07-30 11:21:51","extension":"png","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":558573,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 18\u003c/strong\u003e: Variation in ITS with different blends of RAP with varying percentage GGBS\u003c/p\u003e","description":"","filename":"floatimage23.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/9045e0e121f40e8a9e276b88.png"},{"id":87918022,"identity":"09db390a-c173-4d39-828b-05ae3a22d572","added_by":"auto","created_at":"2025-07-30 11:21:49","extension":"png","order_by":24,"title":"Figure 24","display":"","copyAsset":false,"role":"figure","size":830786,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 19:\u003c/strong\u003eVariation in CBR with different blends of RAP with varying percentage Cement\u003c/p\u003e","description":"","filename":"floatimage24.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/587be78c0b4b06b50bacff75.png"},{"id":87919211,"identity":"41f7b670-8000-489f-9b27-714f0170a87c","added_by":"auto","created_at":"2025-07-30 11:29:49","extension":"png","order_by":25,"title":"Figure 25","display":"","copyAsset":false,"role":"figure","size":847020,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 20:\u003c/strong\u003eVariation in CBR with different blends of RAP with varying percentage Flyash\u003c/p\u003e","description":"","filename":"floatimage25.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/e28652a1d78f6fc19b09bebf.png"},{"id":87918026,"identity":"e3bb138a-6130-4242-b349-3f4f246789bc","added_by":"auto","created_at":"2025-07-30 11:21:49","extension":"png","order_by":26,"title":"Figure 26","display":"","copyAsset":false,"role":"figure","size":93037,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig 21:\u003c/strong\u003eVariation in CBR with different blends of RAP with varying percentage GGBS\u003c/p\u003e","description":"","filename":"floatimage26.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/d239822e79f197adcfc475d9.png"},{"id":87918065,"identity":"17e207a7-893f-4c41-860e-8a309b08e312","added_by":"auto","created_at":"2025-07-30 11:21:51","extension":"png","order_by":27,"title":"Figure 27","display":"","copyAsset":false,"role":"figure","size":666416,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFigure 27:\u003c/strong\u003e Life Cycle Analysis (LCA) of Reclaimed Asphalt Pavement (RAP)\u003c/p\u003e","description":"","filename":"floatimage27.png","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/a3b2df3e7053dccbfdfda19a.png"},{"id":87922201,"identity":"04c97515-6ab2-4936-908b-d7e5f49872dd","added_by":"auto","created_at":"2025-07-30 11:53:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11969935,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6961746/v1/204f3961-de31-4666-b003-82a071c526af.pdf"}],"financialInterests":"","formattedTitle":"Enhancing RAP-Based Pavement Layers with Industrial Byproduct Blends for Improved Performance and Sustainability","fulltext":[{"header":"1. Introduction and background","content":"\u003cp\u003eThe escalating costs, rising demand, and shortages of VA have led to an increased exploration of alternative materials for asphalt pavement. In India alone, approximately 15,000 tonnes of VA are needed for every kilometre of a national highway, as noted by (Aurangzeb and et al \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). However, the concept of reusing old pavement materials is not widely embraced in India, leading to the majority of demolished pavement materials ending up in landfills, which complicates the issue of environmental waste(Arshad M, Ahmed MF 2017) The construction of roads not only requires vast quantities of natural resources globally but also responsible for about 22% of the world's total energy consumption, 25% of fossil fuel usage, 30% of air pollution, and greenhouse gas emissions. However, the production of RAP generates a significant amount of waste, reaching billions of tons annually, as highlighted by the Federal Highway Administration (2008). Furthermore, there is a growing concern on utilizing RAP to mitigate environmental impacts and conserve natural resources worldwide. RAP is essentially a mixture of aggregate bound with asphalt. Research has been conducted on the current challenges of utilizing RAP in pavement base and subbase layers, as highlighted by Milad et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). At the University of California, Berkeley, researchers are developing innovative methods to extract and recycle asphalt binder from RAP using microwave technology. This approach could enhance the quality and consistency of RAP, making it more suitable for high-performance asphalt mixtures, as detailed by Bleakley and Cosentino (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Currently, there is an urgent requirement to classify the available RAP for its subsequent essential applications in road construction. Research by Arshad M and Ahmed ME in (2017) highlighted that RAP exhibits good thermal stability, meaning it performs well across a wide temperature range. This stability is attributed to the asphalt binder in RAP being less affected by temperature fluctuations compared to new asphalt binder. Hence, replacing virgin asphalt (VA) with 100% RAP leads to lower strength but increased resistance to creep and permanent deformations. Nevertheless, RAP can be effectively used in conjunction with natural aggregates, blended with cement, or combined with other additives such as fly ash or geocells, as demonstrated in various studies of (Saride et al. 2010). This research explores the importance of blending RAP with fly ash, cement, and (GGBS) to achieve specific properties of VA. For instance, blending RAP with cement is a common strategy in pavement construction to enhance the strength and durability of the pavement (Taha et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e1999\u003c/span\u003e) When cement is introduced into fine fractions of RAP, it reacts with the mineral components as well as with the residual asphalt binder, affecting the material's strength and durability. The reaction is mainly influenced by amorphous silica, mineral fines, and aged asphalt. In the case of amorphous silica present in the fine RAP particles, it can engage in pozzolanic reactions with cement to produce calcium silicate hydrate (C-S-H) gel, which increases cohesion and strength. The cement serves as a binding agent, securing the RAP particles together and boosting the pavement's overall strength. This approach has been found to significantly improve the performance of pavement in terms of resistance to rutting, cracking, and fatigue. Such enhanced performance results in reduced maintenance costs and a longer lifespan for the pavement, making it a popular choice in pavement construction, expected to grow in the coming years (Ebrahim Abu El-Maaty Behiry 2013).\u003c/p\u003e\u003cp\u003eThe addition of fly ash increases the strength of the mix, primarily depending on the type, curing period, and nature of the activator used (Jayakody et al \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This is because fly ash possesses pozzolanic properties. In the presence of moisture, fly ash reacts with calcium hydroxide to form cementitious compounds. These reactions enable fly ash to enhance the strength and durability of asphalt pavement (Athanasopoulou 2014). Furthermore, fly ash particles are very small, typically less than 10 microns in size, making them an effective mineral filler in asphalt mixtures (Saride et al. 2016). These materials fill the gaps between larger aggregate particles, thereby improving the packing density of the mix. Additionally, fly ash increases the strength and stiffness of the both base and subbase layers, reducing issues such as rutting and fatigue cracking that can occur due to dynamic loads. When blended with mixtures, calcium oxide reacts with the silica present in RAP, forming hydrated products that increase the strength and stiffness of the pavement layers. The availability of silica in RAP may influence the whole study, subject to its nature and reactivity. When the silica is of amorphous nature, it can easily take part in pozzolanic reactions, promoting cementation when RAP is incorporated in cement-based products such as recycled asphalt concrete or asphalt-treated base layers. This can enhance bonding, strength, and durability in the resultant mix.\u003c/p\u003e\u003cp\u003eGGBS, a by-product of the iron and steel industry, has been widely utilized as a partial substitute for Portland cement in pavement construction. Its high resistance to chemical and sulphate attacks contributes significantly to the increased durability of pavements. Additionally, GGBS enhances the resistance to alkali-silica reaction, a leading cause of pavement deterioration. By adding GGBS, pavements can also become stronger, as it aids in the formation of additional calcium silicate hydrates (C-S-H) in concrete. RAP is a mixture of asphalt binder and aggregate, both of which are known for their strength and durability. RAP is a granulated composite geomaterial that exhibits high activity even under normal atmospheric conditions (Abraham SM, Ransinchung GDRN (2018). The use of RAP not only reduces overall construction costs but also ensures the efficient use of available resources. Studies have shown that the incorporation of RAP into pavements, up to a maximum of 30% in base layers, has been successful. However, achieving the desired performance with RAP content above 30% requires careful selection of supplementary additives. Successful replacement of VA with RAP has been attributed to factors such as the binder content, well-graded aggregates, and effective mix design.\u003c/p\u003e\u003cp\u003eThe application of RAP materials in pavement construction offers benefits like lower material costs, conservation of aggregate resources, reduction in disposal costs, and elimination of waste from landfills (Khan et al \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The usage of RAP as an alternative to virgin materials is very environmentally friendly, especially in lowering greenhouse gas (GHG) emissions. Virgin asphalt manufacturing involves energy-intensive processes such as raw material extraction, transportation, and heating of raw materials like aggregates and bitumen. All these processes release considerable amounts of CO₂. Conversely, RAP minimizes the requirement for new raw materials by recycling old asphalt, reducing energy consumption and minimizing the emission related to the processing of materials. Furthermore, using RAP in pavement construction eliminates the need for landfilling aged asphalt, avoiding methane and other pollutants release from decomposing waste materials. The transportation emissions are also minimized as less virgin aggregate needs to be extracted and transported over long distances. Additionally, the application of RAP in warm mix asphalt (WMA) technologies also reduces emissions further by allowing the production of asphalt at temperatures lower than conventional methods, consuming less fuel and less air pollution. In general, incorporating RAP into asphalt mixture results in a greener construction practice through natural resource conservation, minimized carbon footprints, and the advancement of circular economy concepts in road construction.\u003c/p\u003e\u003cp\u003eStorage and handling of RAP materials pose some challenges. One of the major issues is keeping the quality of the RAP intact over a period of time, as it is prone to contamination with extraneous materials such as soil, debris, or organic material, which can reduce its performance during subsequent use. It is reported in a study that RAP contamination may have considerable impact on the mix's general properties, e.g., binder content and aggregate gradation, to make it more difficult to attain the preferred asphalt mixture. Furthermore, inappropriate storage can lead to the degradation of the RAP's quality, especially if exposed to excessive moisture or harsh weather conditions, which would impact its functionality to mix well with virgin material when repaving. Kim et al. (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) identified in their research that variability in RAP materials may cause inconsistency in mix performance, which may cause construction quality control to be challenging. These issues can cause inconsistencies in the final quality of the pavement.\u003c/p\u003e\u003cp\u003eTo ensure the quality and usability of RAP materials in new asphalt mixtures, it is crucial to implement proper storage facilities, effective quality control measures, and accurate testing procedures. Various evaluations have been conducted to assess the mechanical and engineering characteristics of both aged and fresh RAP, along with their combinations with VA. These assessments include sieve analysis, specific gravity measurement, flakiness index, elongation index, water absorption, and pH analysis. Additionally, impact, abrasion, and compressive strength tests have been carried out to examine the performance of different pavement mix compositions.\u003c/p\u003e\u003cp\u003eThis study primarily focuses on identifying the optimal proportion of RAP blended with cement, fly ash, and GGBS for pavement base layers. The chemical composition of RAP materials was analyzed using X-ray fluorescence (XRF) to detect primary minerals and potential impurities. Fourier Transform Infrared Spectroscopy (FT-IR) was utilized to examine the chemical properties of the asphalt binder, providing insights into oxidation, aging, and the presence of additives. Moreover, key engineering parameters such as optimum moisture content (OMC), maximum dry density (MDD), unconfined compressive strength (UCS), California Bearing Ratio (CBR), indirect tensile strength (ITS), and Marshall Stability were investigated to determine the feasibility of RAP mixes for pavement construction.\u003c/p\u003e"},{"header":"2. Material used","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Collection of materials\u003c/h2\u003e\u003cp\u003eThe primary ingredients utilized in various tests include Ordinary Portland Cement (Grade 33), Fly Ash (Class C), GGBS, RAP), and VA. The primary properties of these raw materials were initially assessed through preliminary tests according to both ASTM and Indian Standards. The Ordinary Portland Cement (Grade 33) was sourced from a cement factory in Chettinadu. The impact of RAP on cement properties varies significantly, dependent on factors such as RAP quality and quantity, cement composition and curing conditions, and cement specific gravity (2.5 to 3.5). The concrete produced meets the IS 4031-3 standard with a soundness value of 0.4mm. Fly Ash, produced in Mettur Thermal Power Plant, Mettur, with coordinates 11\u0026deg;30'17.1936\"N 77\u0026deg;14'18.2256\"E, was collected in the wet state and stored in the open to reduce moisture content before being processed in the lab. The collected raw materials were then transported to the laboratory, where they were placed in a dehumidified environment to further reduce moisture content prior to being subjected to characterization tests. According to IS: 2386 (PART III), fly ash typically has a specific gravity of 2.28.\u003c/p\u003e\u003cp\u003eFlyash,waste product of coal burning in thermal power facilities, is an important component of asphalt mixtures due to its contribution to their performance and sustainability. As a mineral filler or modifier, fly ash increases the strength and durability of the mixture, rendering it more resistant to rutting, fatigue cracking, and moisture damage. It also increases workability, enabling more effective compaction and fewer air voids, which result in longer pavement life. GGBS, on the other hand, is a by-product of blast furnace melting, rapidly cooled (e.g. by immersion in water), and possesses a specific gravity of 2.85 and soundness value of 0.3mm, all satisfying IS 4031-3 standards. Recycled Aggregate (RAP), collected from various sites in Sathyamangalam, Erode district, between 11\u0026deg;30'17.1936\"N and 77\u0026deg;14'18.2256\"E, about 10 tons from four different locations were collected for the study. Virgin Aggregate (VA), on the other hand, was obtained from a construction site at the Bannari Amman Institute of Technology College in Erode district, with coordinates 11.4986\u0026deg;N and 77.2743\u0026deg;E. According to Tighe SL et al. (2015), the use of VA in construction projects plays a crucial role in enhancing the mechanical properties of concrete, as their original nature often leads to superior strength and durability. The color of RAP changes from dark and grey in wet conditions to a lighter grey in dry conditions, and it does not appear black, but rather slightly bitumen-coated. This observation aligns with the findings of Giani MI et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), who noted similar color variations in RAP materials depending on moisture levels, indicating potential impacts on workability and compaction. The physical characteristics of RAP were also determined through basic laboratory tests. Studies by Al-Suhaibani and Mamlouk (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) emphasize that laboratory evaluations of RAP are fundamental for assessing its potential as a substitute in concrete mixes, particularly for its strength and gradation properties.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Methodology\u003c/h2\u003e\u003cp\u003eFor enhanced strength and hardness of concrete, various mix proportions of VA and RAP were used to create test mixes. They were tested both with and without cementing material like OPC, Class C Fly Ash, and GGBS to find their effect on the mechanical characteristics. The research was interested in how different proportions of RAP and VA, when stabilized with these binders, impacted the strength and long-term behavior of the concrete. A systematic approach was followed to develop blend ratios from fully recycled aggregates to fully virgin aggregates, allowing for a thorough performance evaluation. Five particular blends were tested: 100% RAP, 75% RAP with 25% VA, 50% RAP with 50% VA, 25% RAP with 75% VA, and 100% VA. Stabilizers were added to the blends in an effort to maximize durability and mechanical strength. The stabilizers used were OPC, which enhances early strength gain and structural stability; Class C Fly Ash, which enhances workability, durability, and long-term strength and minimizes permeability; and GGBS, an industrial byproduct, which enhances durability, reduces heat of hydration, and boosts sulfate resistance. By incorporating these stabilizers, the research sought to create an ideal RAP-VA mixture for sustainable and high-strength concrete applications.\u003c/p\u003e\u003cp\u003eEfficient blending is essential in deciding the right RAP content in asphalt mixtures, as it influences the interaction between aged RAP binder and virgin binder. Inefficient blending may result in improper binder content calculations, causing mixtures to be too stiff or too soft, which undermines pavement performance. Huang et al. (2014) examined the efficiency of blending RAP using rheological properties and molecular weight distributions. Their research showed that longer mixing time and higher temperature improved blending between virgin binder and RAP to a maximum blending ratio of slightly less than 80%. This result highlights the need to optimize mixing conditions to enhance blending efficiency. They concluded that an increase in mixing time and temperature resulted in more blending in the RAP/RAS mixture. Nevertheless, mobilization rate of RAP binder reduced with an increase in percentages of RAP, which shows that not all aged binder becomes active in the mix.\u003c/p\u003e\u003cp\u003eThese stabilizers were added to the concrete mixture in different proportions of 3%, 5%, and 7% of the weight of the entire mix. The main aim of this stabilization was to counteract possible weaknesses due to the addition of RAP, including lower bonding strength and increased moisture susceptibility. Besides, the stabilizers also helped in enhancing cohesion, compressive strength, and durability in general to ensure that the produced concrete would be suitable for performance requirements across a range of structural applications.\u003c/p\u003e\u003cp\u003eRAP-VA mixes were evaluated using an extensive set of tests to evaluate their physical, mechanical, and durability properties. The purpose of these tests was to find the ideal blend of RAP-VA and the most suitable cementitious stabilizer dosage to achieve improved pavement performance. Physical characterization of aggregates was done by sieve analysis, which identified the particle size distribution to ensure that the gradation satisfied the specifications of base layers. Specific gravity tests enabled quantification of RAP and VA relative density, impacting mix design and compaction (AASHTO 2021). The flakiness and elongation index tests were conducted to determine aggregates' shape characteristics, as flaky or elongated particles may impair interlocking and compaction. Water absorption tests evaluated the aggregates' susceptibility to moisture, which is vital for mix durability, particularly in mixes containing RAP. The pH test was performed to assess the alkalinity or acidity of the aggregate mix since high pH levels can affect the hydration process of cementitious binders.\u003c/p\u003e\u003cp\u003eTo find out the mechanical resistance and degradation strength, impact and abrasion testing was conducted. The Aggregate Impact Value test assessed the sudden impact resistance of aggregates, an important parameter of base courses experiencing dynamic loads. The Los Angeles Abrasion test determined RAP-VA blends' resistance to wear such that they remained capable of facing repeated traffic. Compressive strength tests gave information about the capacity of stabilized RAP mixtures to withstand axial loads, which is critical for pavement longevity. The Unconfined Compressive Strength (UCS) test, performed on specimens with different RAP content and different dosages of stabilizer (3%, 5%, and 7%), showed how cementitious materials improved cohesion and load-carrying capacity. Increased UCS represented enhanced stabilization, whereas decreased UCS represented the necessity for optimization of binder content.\u003c/p\u003e\u003cp\u003eWith respect to performance-based testing, the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) tests were performed to quantify the optimal moisture and compaction values for maximum strength. The California Bearing Ratio (CBR) test was employed to evaluate the resistance to traffic loads of the RAP-VA mixtures, which is essential for their base layer applicability. Increased CBR values were representative of greater strength and traffic load deformation resistance. The Indirect Tensile Strength (ITS) test tested the tensile characteristics of the mixes, which are critical to avoiding cracking and fatigue failure. Finally, the Marshall Stability test was conducted to determine the load resistance of the RAP-VA blends to deformation, ensuring that the mixture would be structurally sound under vehicular stresses. Results of these tests altogether informed the choice of the best RAP percentage and stabilizer dose so as to strike a balance between sustainability and performance for pavement use.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Graphical Methodology`\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Material characterization","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Reclaimed Asphalt Pavement (RAP) And Virgin Aggregate(VA)\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe physical characteristics of RAP and VA were assessed to make sure that satisfy the fundamental requirements set by the Indian codes. This evaluation included tests such as sieve analysis, Specific gravity, Flakiness Index, and Elongation Index (Augusto Cannone Falchetto 2019). Moreover, the ability of RAP to absorb water and its pH levels were also checked. The proportion of different particle sizes in RAP can significantly affect its performance when added to new mixtures.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e3.1.1 Gradation analysis of RAP\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eUsually, the particle size distribution of RAP is coarser than that of VA because the asphalt binders deteriorate as the pavement ages (De Lira RR et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). To measure the size distribution of RAP, sieve analysis was performed in both old RAP (stored for months) and newly RAP (the pavement material was shortly after its installation), along with VA according to IS: 2386 (PART II) to calculate the parameters of Uniformity Coefficient (Cu) and Curvature Coefficient (Cc). Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e present the results of the sieve analysis for both the aged and newly damaged RAP. It is essential to carefully control and modify the particle size distribution of RAP to ensure that it matches the requirements of the new asphalt mix design for optimal performance.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eGradation analysis of Old RAP\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSieve size(mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMass of soil retained (g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePercent mass retained (g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCumulative percentage retained (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePercentage finer (n)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e226\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e22.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e77.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e415\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e64.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e35.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e147\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e78.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e21.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e172\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e17.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eGradation analysis of New RAP\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSieve size(mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMass of soil retained (g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePercent mass retained (g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCumulative percentage retained (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePercentage finer (n)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e84\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e390\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFrom above Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e it is clear that Sieve analysis of RAP typically reveals a particle size distribution that indicates the quality and suitability of the material for reuse in asphalt mixtures. In a typical result, the largest sieve size (40 mm) shows 0% weight retained, with a gradual increase in weight retained as the sieve size decreases. The particle size of RAP has a considerable impact on the behavior of asphalt mixtures subjected to repeated loading. Coarse RAP particles can improve aggregate interlock, enhancing load distribution and structural strength. On the other hand, fine RAP particles raise the surface area covered with aged binder, which can result in greater stiffness and lower fatigue resistance as a result of poor blending with virgin materials. For instance, at the 12.5 mm sieve, approximately 35.9% of the material is retained, while the 10 mm sieve retains about 21.2%. These results are crucial for determining the gradation of RAP and ensuring it meets the specifications for incorporation into new asphalt mixtures, ultimately contributing to sustainable construction practices. Changing the gradation of RAP can make a significant difference in the durability and workability of the asphalt mixture. For coarser gradation, usually occurring with older RAP, greater particles make the mixture stiffer, more difficult to compact, and less workable because of increased friction between the particles. This can create challenges in ensuring good compaction when the asphalt is installed, resulting in problems such as a non-level surface. Conversely, finer gradation, which commonly exists in newly broken RAP, can enhance workability through increased lubrication between aggregates, which makes it easier to compact and results in a smoother surface.\u003c/p\u003e\u003cp\u003eIn terms of durability, coarse gradation is likely to have a negative impact, in that large particles tend to compromise adhesion between asphalt binder and aggregates. This might contribute to increased void content in the mix, lower density, and increased permeability, ultimately causing earlier wear and greater vulnerability to water damage. Conversely, finer gradation enhances binder adhesion and yields higher density, which minimizes the voids and enhances the mix's resistance to moisture damage, cracking, and fatigue. The improved binder coverage also enhances the overall resistance to rutting and cracking, which helps to make the asphalt pavement more durable.\u003c/p\u003e\u003cp\u003eMoreover, gradation influences the mix's consistency and uniformity. Coarse gradation can cause inconsistency in the behavior of the material, making it more difficult to have an even distribution of binder, whereas finer gradation provides more uniform performance because of the more even particle size. Additionally, a finer gradation will usually use less binder to provide adequate coating of the aggregates, which can result in cost savings. In exceeds 50%, the gradation of RAP is very influential in establishing workability, toughness, and total performance of asphalt mix, finer gradation, in most instances, tending to produce favorable mix properties as well as sustained performance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e3.1.2 Water absorption test of RAP\u003c/h2\u003e\u003cp\u003eThe absorption test for RAP is a method used to evaluate the porosity of RAP or asphalt materials. This test assesses the ability of RAP to withstand adhesive strength under heavy loads, helping to determine its capacity to absorb water. This absorption can significantly impact the material's durability and performance. Durability of materials was conducted to measure the amount of water absorbed by RAP, falling within the range specified by IS:2386 (PART I-VII) from 0.1 to 2. A lower absorption percentage indicates a denser, more durable material, whereas a higher percentage suggests a more porous material that may be more vulnerable to damage from water and other environmental factors. The water absorption values for old and new RAP were found to be 1.5 and 1.2, respectively. Typically, materials with water absorption (VA) of 0.65\u0026ndash;2.0%, falling within the range of 0.5\u0026ndash;2.0%, are considered to be of higher quality(Arulrajah and piratheepan 2014) This is because they are free from aged binders and contaminants, offering a more uniform and predictable performance in asphalt mixtures. However, the presence of bitumen in RAP can affect its water absorption. The surface of the aggregate also plays a role in this phenomenon. According to Brown et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2009\u003c/span\u003e), aggregate surface texture can significantly influence binder adhesion and moisture resistance in asphalt mixtures. On the other hand, RAP is more likely to exhibit higher absorption values, ranging from 1.5\u0026ndash;4.5%, due to the aging of asphalt binders and potential degradation of the original aggregates (Pavement Recycling Guidelines, FHWA, 2011). This increased absorption in RAP can alter the overall binder content of the mix, necessitating adjustments to ensure an adequate supply of new binder for proper coating and bonding (Mcdaniel and Anderson \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2001\u003c/span\u003e)While virgin aggregates absorb less water, reducing the risk of moisture-related issues (Roberts FL et al \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1996\u003c/span\u003e), the higher water absorption of RAP requires careful consideration in mix design to mitigate potential moisture damage (Huang et al 2005). Therefore, while RAP contributes to sustainability in asphalt production (Hansen K R, Copeland A 2017), its higher and variable water absorption values demand meticulous management in mix design to ensure the pavement performs optimally (Shirodkar et al \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3 Elongation and flakiness test of RAP\u003c/h2\u003e\u003cp\u003eThe elongation index of an aggregate is a key measure that determines the percentage of particles, by weight, whose length exceeds four-fifths of their mean dimension. According to (Mohammadinia A et al \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), elongated aggregates may compromise the structural integrity of pavements, as they tend to break under heavy loads due to their slenderness. This property is of particular interest when comparing RAP and (VA). For calculating the elongation properties, RAP and VA particles are subjected to standard procedures, such as the use of a 63 mm sieve, which retains particles larger than 6.3 mm. In compliance with IRC (Indian Roads Congress) recommendations, the elongation index for various types of pavements is typically limited to 25%. Higher values may indicate a potential for material instability under dynamic loads, a point echoed by (Khanna and Justo \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). However, before conducting the elongation index test, a flakiness test is crucial, as flaky particles can introduce inherent weaknesses in the aggregate structure. According to Airey et al. (2008), flaky particles, due to their thin structure, are more prone to breakage, potentially leading to material failure when subjected to heavy traffic or load stresses. The properties in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, which compare the flakiness and elongation indices of RAP and VA, underscore the significance of these tests in ensuring material durability. As supported by Roberts et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1996\u003c/span\u003e), understanding the flakiness and elongation of aggregates is essential for optimizing the performance of pavements, particularly when recycled materials like RAP are used.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFlakiness and Elongation index of RAP compare with VA\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProperties\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOld RAP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNew RAP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eVA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eIRC recommendation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eFlakiness index\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e33.76%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e40.57%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e18.11%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e35%(IS 2386 (Part 1):1963\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eElongation index\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e23.11%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e25.4%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e17.11%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e reveals that the flakiness index of RAP is generally higher compared to VA. This is because VA, with their more uniform, cubical shapes resulting from controlled processing methods, typically exhibit lower flakiness index values, ranging from 10\u0026ndash;25% [54]. Studies by Sivakumar and Jain (2010) also support that virgin aggregates exhibit a more cubical shape due to precision in manufacturing processes, contributing to their lower flakiness indices. On the other hand, RAP's flakiness index values can range from 20\u0026ndash;40%, due to the milling and crushing processes used in its recovery, which often produce more flat and elongated particles. This observation is in line with Croteau and Tessier (2008), who emphasized the impact of milling operations on the shape of RAP particles. According to Kandhal P S and Mallick R B (1997), flakiness in RAP can adversely affect the compaction, stability, and load-bearing capacity of asphalt mixes, potentially leading to pavements that are weaker and less durable. However, it's important to note that the flakiness index values are within the acceptable range according to IRC guidelines, which means that careful adjustments in mix design and compaction techniques are necessary to ensure optimal pavement performance. Studies by Huang et al. (2005) also indicate that although RAP has a higher flakiness index, mix design adjustments can mitigate the effects.\u003c/p\u003e\u003cp\u003eAdditionally, the elongation index of RAP is typically higher than that of virgin aggregates. VA usually have lower elongation index values, typically ranging from 5\u0026ndash;20%, due to their controlled production processes that yield more cubical and uniformly shaped particles. In contrast, RAP often exhibits higher elongation index values, typically ranging from 15\u0026ndash;35%, as the milling and crushing processes involved in its recovery can produce more elongated particles. Gonz\u0026aacute;lez-Le\u0026oacute;n et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) also observed that the elongation index in RAP influences compaction behavior due to elongated particles.\u003c/p\u003e\u003cp\u003eThese higher elongation values in RAP can negatively impact the compaction and interlocking characteristics of asphalt mixes, potentially reducing their stability and load-bearing capacity. Elongated particles in RAP can lead to increased voids and decreased structural integrity, necessitating careful adjustments in mix design and compaction practices to ensure the performance of pavement and durability.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e3.1.3 Specific gravity test of RAP\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eRAP is primarily defined by its rigidity and strength rather than its elasticity or deformability. However, these characteristics are influenced by factors such as the age and condition of the original pavement. As shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, the specific gravity of both old and new RAP aligns with the range specified in IS: 2386 (Part III). Specific gravity, which varies based on material composition and manufacturing conditions, typically ranges between 2.0 and 2.4 for RAP. This is comparable to the specific gravity of virgin asphalt (VA) mixtures, further supporting RAP's suitability as a material in road construction.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSpecific gravity of RAP combinations with VA\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix proportions\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100% RAP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e75%RAP\u0026thinsp;+\u0026thinsp;25% VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e50%RAP\u0026thinsp;+\u0026thinsp;50% VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25%RAP\u0026thinsp;+\u0026thinsp;75% VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100 VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eAs per IS: 2386(PART 1)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eOld RAP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e2.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.5 to 3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNew RAP\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.5 to 3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe specific gravity of the RAP may be affected by gradation, the type and quantity of binder, contaminants, or other materials. The specific gravity may also change over time due to aging or weathering.\u003c/p\u003e\u003cp\u003eThe specific gravity measurements of the old RAP ranged from 2.33 in the 100% RAP mix to 2.65 in the 50% RAP\u0026thinsp;+\u0026thinsp;50% VA and 100% VA mixes, consistent with the recommended range of 2.5 to 3. Likewise, the specific gravity of the new RAP varied from 2.09 in the 75% RAP\u0026thinsp;+\u0026thinsp;25% VA mix to 2.60 in the 25% RAP\u0026thinsp;+\u0026thinsp;75% VA mix. Though the older RAP values generally complied with the specified requirements, the new RAP registered some variations, especially in the 75% RAP\u0026thinsp;+\u0026thinsp;25% VA mix that had the lowest specific gravity of 2.09. The variations point out that the addition of VA to the mix enhances the general density and stability, especially in the 50% RAP\u0026thinsp;+\u0026thinsp;50% VA and 25% RAP\u0026thinsp;+\u0026thinsp;75% VA mixes. The results indicate that the use of a balanced ratio of RAP and VA improves the quality of the mix and also ensures standard specification compliance.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e3.1.4 pH value of RAP\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe pH values of both old and new RAP are measured at 8.6 and 8.5, respectively, aligning with the acceptable range specified for asphalt materials. As per IRC 015-2011, which provides guidelines for materials in road construction, the optimal pH range for asphalt is 8.6 to 8.9 to ensure stability and durability. Ayan et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) underscore the significance of evaluating the chemical and physical properties of recycled aggregates to ensure their compatibility with virgin materials. Their research highlights that understanding chemical characteristics, such as pH, is crucial for maintaining the integrity and performance of asphalt mixtures. The results indicate that both old and new RAP exhibit similar chemical properties to virgin asphalt (VA), particularly in terms of alkalinity, confirming their suitability for reuse in road construction.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\u003ch2\u003e3.1.5 Chemical composition analysis using X-ray Fluorescence (XRF) test\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eX-ray Fluorescence (XRF) analysis of RAP is a critical analytical method employed to ascertain the elemental content of its aggregates and binder. The test assists in the identification of the major oxides including silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), calcium oxide (CaO), and iron oxide (Fe₂O₃), which affect the mechanical characteristics of the pavement material. Moreover, XRF is capable of identifying trace metals such as lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr), which could be signs of contamination from industrial or traffic sources. The analysis also offers information on binder aging through the detection of elemental changes that are indicative of oxidation and degradation over time. Knowledge of the chemical composition of RAP from XRF analysis is important for maximizing its reuse on road construction, maintaining quality control, and reducing environmental effects. This study was conducted at the Ceramic Research Centre in Chennai. Common minerals identified include silica, aluminium oxide, sulfur trioxide, potassium oxide, calcium oxide, and various clays, all of which significantly impact the material's properties and performance. As reported by Kumar et al. (2017), the presence of these minerals in RAP plays a critical role in determining its physical and mechanical behavior. The silica content in RAP is considerably higher than that of aluminium oxide, sulfur trioxide, and potassium oxide. Silica enhances pavement strength and durability by forming a robust cementitious matrix, as supported by the findings of Zhang and Liu (2019), who highlighted silica's role in improving the load-bearing capacity of recycled asphalt. Aluminium oxide increases hardness and wear resistance, improving durability under heavy traffic. Conversely, sulfur trioxide can be harmful as it may form expansive compounds like gypsum or ettringite, leading to cracking and structural degradation Potassium oxide, beneficial in small quantities for regulating cement setting time, can cause alkali-silica reaction when present in excess, resulting in severe cracking and pavement deterioration. The research by Raguraman Vaithiyasubramanian et al. (2025) emphasizes the importance of controlling potassium oxide levels to mitigate alkali-silica reaction risks and maintain pavement integrity. Balancing these components is vital for maintaining pavement longevity and reliability. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e depicts the XRF curve for Percentage Variation in concentration vs compound of RAP material\u003c/p\u003e\u003cp\u003eThe results of the XRF analysis reveal that SiO₂ (silicon dioxide) predominates in percentage composition, followed by Al₂O₃ (aluminum oxide) and CaO (calcium oxide), while Fe₂O₃ (iron oxide) has the highest concentration in ppm in the trace elements. The elemental composition influences the mechanical and durability characteristics of the material substantially; thus, it can be applied to engineering and construction uses.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe existence of SiO₂ helps to add strength and durability by engaging in pozzolanic reactions with calcium hydroxide Ca(OH)2, forming more calcium silicate hydrate (C-S-H) gel, strengthening the binding characteristics of the material\u003c/p\u003e\u003cp\u003eSiO₂ + Ca(OH)\u003csub\u003e2\u003c/sub\u003e\u0026rarr;C-S-H (gel)\u003c/p\u003e\u003cp\u003eThe Al₂O₃ present may react with sulfates and calcium hydroxide in cementitious materials to form calcium aluminate hydrates (CAH), enhancing durability\u003c/p\u003e\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003e​O\u003csub\u003e3\u003c/sub\u003e​+Ca(OH)\u003csub\u003e2\u003c/sub\u003e​+H2​O\u0026rarr;CAH\u003c/p\u003e\u003cp\u003eMoreover, high levels of Fe₂O₃ indicate the material's ability to offer enhanced resistance to degradation within the environment, as the material is able to react with calcium substances, which form ferrite phases to ensure material stability\u003c/p\u003e\u003cp\u003eFe\u003csub\u003e2\u003c/sub\u003e​O\u003csub\u003e3\u003c/sub\u003e​+CaO\u0026rarr;C-F (Calcium Ferrite)\u003c/p\u003e\u003cp\u003eThe availability of CaO shows scope for hydration reactions, which play a role in setting and hardening\u003c/p\u003e\u003cp\u003eCaO\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2​\u003c/sub\u003eO\u0026rarr;Ca(OH\u003csub\u003e)2\u003c/sub\u003e​\u003c/p\u003e\u003cp\u003eGenerally, the XRF analysis indicates that the material possesses high pozzolanic activity, high durability, and is appropriate for cementitious and pavement use, based on the chemical reactions between silica, alumina, iron oxides, and calcium compounds.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\u003ch2\u003e3.1.6 Fourier Transform Infrared (FTIR) analysis\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eFourier Transform Infrared (FTIR) spectroscopy is an important analytical technique to evaluate the chemical content and aging impact in Reclaimed Asphalt Pavement (RAP) binders. It detects oxidation indicators like carbonyl (C\u0026thinsp;=\u0026thinsp;O) at ~\u0026thinsp;1700 cm⁻\u0026sup1;, sulfoxide (S\u0026thinsp;=\u0026thinsp;O) at ~\u0026thinsp;1030 cm⁻\u0026sup1;, and hydroxyl (-OH) at ~\u0026thinsp;3400 cm⁻\u0026sup1;, which are signs of binder aging as a result of long-term exposure to heat, oxygen, UV radiation, and water. The height of such peaks in the FTIR spectrum assists in measuring the level of binder hardening and the possibility of RAP reuse in fresh asphalt mix. FTIR also assesses the efficiency of mixing aged RAP binder with fresh binder by examining their spectra. A large gap between the mixed and new binder spectra shows low integration, calling for the use of rejuvenators to enhance compatibility. Carbonyl index (CI) and sulfoxide index (SI) measure the changes in oxidation for optimal RAP content in long-term and lasting asphalt mixtures.\u003c/p\u003e\u003cp\u003eThe FTIR analysis methodology starts from sampling and drying at temperatures less than 60\u0026deg;C for moisture removal without changing the chemical nature of the binder. The aged binder is next recovered from solvents such as trichloroethylene (TCE), toluene, or ethanol using Soxhlet extraction, centrifugation, or reflux techniques. Following extraction, fine particles are eliminated through filtration, and the solvent is driven off by rotary evaporation or vacuum drying under temperatures not exceeding 110\u0026deg;C to avoid thermal degradation. The binder recovered is examined either by the potassium bromide (KBr) pellet method, in which a translucent pellet is formed for transmission mode analysis, or by the Attenuated Total Reflectance (ATR) method, in which the sample is placed directly on the ATR crystal for ready, non-destructive examination.\u003c/p\u003e\u003cp\u003eFTIR spectroscopic analysis is performed on a SHIMADZU IRAffinity-1S FTIR Spectrophotometer equipped with a MIRacle10 Single Reflectance ATR accessory. The spectra are captured at a resolution of 4 cm⁻\u0026sup1; with 25 scans between 400\u0026ndash;4000 cm⁻\u0026sup1;, which gives thorough information regarding the chemical composition and aging behavior of RAP binders. FTIR is a crucial technique for sustainable asphalt pavement management as it facilitates efficient binder rejuvenation and maximum RAP usage in new mixtures.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe provided image is an FTIR (Fourier Transform Infrared) spectrum, recorded using a SHIMADZU IRAffinity-1S spectrophotometer, from the Department of Chemistry at Bannari Amman Institute of Technology. The sample code is labeled \"OLDROCK,\" suggesting that the material analyzed is an aged or weathered rock sample. The spectrum plots transmittance (%T) against wavenumber (cm⁻\u0026sup1;), spanning from 4000 cm⁻\u0026sup1; to 400 cm⁻\u0026sup1;, which is the typical mid-infrared range for FTIR analysis. Key absorption peaks are observed at specific wavenumbers, indicating the presence of various functional groups in the sample.\u003c/p\u003e\u003cp\u003eSignificant peaks include a broad absorption band around 3741.90 cm⁻\u0026sup1; and 3936.71 cm⁻\u0026sup1;, which are characteristic of hydroxyl (-OH) stretching vibrations, suggesting the presence of water molecules or hydroxyl-containing minerals. The peaks at 2921.16 cm⁻\u0026sup1; and 2357.01 cm⁻\u0026sup1; could be attributed to C-H stretching vibrations, commonly found in organic compounds, or CO₂ asymmetric stretching, which is often present in carbonate minerals or atmospheric interference. The region around 561.29 cm⁻\u0026sup1;, 509.21 cm⁻\u0026sup1;, 483.71 cm⁻\u0026sup1;, and 430.31 cm⁻\u0026sup1; typically corresponds to metal-oxygen stretching vibrations, indicative of silicates or other metal-containing minerals. The data from this FTIR spectrum provides valuable insight into the chemical composition of the \"OLDROCK\" sample, aiding in the identification of minerals, the presence of organic matter, or possible environmental effects such as weathering or contamination. By analysing the characteristic absorption bands, researchers can determine the sample\u0026rsquo;s mineralogical and chemical properties, making it useful for geological, environmental, and material science applications. Further comparison with standard FTIR spectra databases can help refine the interpretation of the observed peaks and confirm the presence of specific compounds.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe FTIR (Fourier Transform Infrared) spectral analysis of sample NEWROCK, as carried out at 14:18:52 with a Shimadzu FTIR spectrometer in the Department of Chemistry, Bannari Amman Institute of Technology, indicates the presence of functional groups in the sample through characteristic absorption bands pointing towards the occurrence of different molecular vibrations. A wide peak at 3745.76 cm⁻\u0026sup1; indicates the presence of hydroxyl (-OH) groups, which are often present in alcohols or water molecules. The peak at 2922.16 cm⁻\u0026sup1; is due to C-H stretching, which is indicative of aliphatic hydrocarbons. A sharp absorption at 2360.87 cm⁻\u0026sup1; may be due to atmospheric CO₂. Also, a strong absorption at 1654.28 cm⁻\u0026sup1; is due to the C\u0026thinsp;=\u0026thinsp;O stretching, which is generally found in ketones, aldehydes, or carboxyl functional groups. The band at 1546.91 cm⁻\u0026sup1; indicates the amide (-NH) groups, and the 1463.97 cm⁻\u0026sup1; band indicates C-H bending vibrations. A sharp band at 1041.56 cm⁻\u0026sup1; indicates the C-O stretching characteristic of alcohols or ethers. Bands in the fingerprint region at 586.36 cm⁻\u0026sup1;, 553.57 cm⁻\u0026sup1;, 509.21 cm⁻\u0026sup1;, and 462.92 cm⁻\u0026sup1; are indicative of the presence of metal-oxygen bonds, which could point towards the presence of inorganic material. The general spectral analysis indicates the presence of hydroxyl, carbonyl, alkane, and potential inorganic functional groups in the sample. More detailed analysis involving methods like X-ray diffraction (XRD) or scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) would be useful for a clearer idea of the sample composition.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"4. Effect of RAP on Pavement characteristics","content":"\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e4.1. Impact test\u003c/h2\u003e\u003cp\u003eThe purpose of this test is to measure the resistance of the material to impact load (impact) and to determine the impact strength. Impact testing is a type of pavement quality test used to determine the suitability of aggregates for pavement construction. In general, RAP has lower impact than virgin asphalt. This decrease in strength is due to the properties of RAP, such as hardness, longer life, and the ability of bones to deteriorate over time. Kim et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and Lee and Kim (2018) added that RAP materials will become less flexible due to aging and environmental exposure, which may cause the adhesive to harden and increase its brittleness, thus affecting its use in high-performance applications. West et al. (\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) discussed that mixing RAP with VA can increase the overall durability and impact of the mixture. This test performs impact tests on five different types of old and new RAP to determine their impact strength. The adverse impact of all composites is measured by testing tests such as the Charpy impact test apparatus described in IS 1757. To determine the impact value of RAP and VA aggregates of the previously selected combination, sizes 10 mm and 2.36 mm. This method allows reliable classification of aggregates according to IS 2386 Part 4 (1963). To obtain consistent results, composite samples were oven dried at 108\u0026deg;C for four hours, a process reminiscent of the work done by Tang et al. (\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) on moisture in measuring power. Samples were crushed into 10mm \u0026times; 12.5 mm fines were sieved through 2.36 mm IS sieve before testing. RAP is usually obtained from old asphalt exposed to weathering, traffic and the environment due to the degradation of asphalt binder, which becomes brittle over time and reduces its impact strength. This behavior has been discussed by Kringos and Scarpas (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), who mentioned the aging process of RAP to reduce its sealing flexibility and increase its brittleness. Improve its properties, including impact strength. According to the Asphalt Association (2019) guidelines, additives such as rejuvenators, polymers and other modifiers can improve the flexibility and performance of old asphalt binders. By adjusting the composition of asphalt mixture containing RAP, impact strength can be optimized for different applications, as suggested by Kim et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), supporting the work of RAP in solving sustainable development problems.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe findings from Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e show that the addition of VA to RAP increases the Aggregate Impact Value (AIV), which enhances aggregate toughness and durability according to IS 2386 (Part IV): 1963, which indicates that lower AIV values reflect better impact resistance. For 100% RAP, AIV is 17% for OLD RAP and 16.64% for New RAP, reflecting comparatively poor toughness. With the addition of VA, however, the AIV reduces gradually, showing enhanced impact resistance. The best proportion is at 50% RAP\u0026thinsp;+\u0026thinsp;50% VA, where the AIV is 12.33%, indicating a good mix composition that increases durability. Beyond this point, at 25% RAP\u0026thinsp;+\u0026thinsp;75% VA, a mild rise in AIV is seen, perhaps the result of mixing variability, so an overloading VA content would not necessarily produce further gains. This underlines the need for a proper balance between RAP and VA by having an ideal RAP-to-VA ratio to attain strength as well as performance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e4.2. Crushing test\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eAggregate crushing strength serves as a critical indicator of an aggregate's resistance to fracture under a progressively applied compressive load, particularly relevant to evaluating material performance in pavement construction. Kandhal and Mallick (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) emphasize the correlation between aggregate strength and pavement durability. Reclaimed asphalt pavement (RAP) exhibits variations in crushing strength due to factors such as its source, recycling methods, and the presence of contaminants or additives. West et al. (\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) highlight that binder aging, oxidation, and aggregate degradation during RAP's service life generally contribute to its lower crushing strength compared to VA. Notably, a total crushing strength exceeding 30 may indicate anomalies or deviations from expected aggregate behavior, as outlined in ASTM D6931 (2007). Refer Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e Experimental results demonstrated that all trial proportions of RAP and VA met the strength requirements specified in IS 2386 Part \u0026ndash; 4 (1963). Specifically, mixtures with 50% RAP\u0026thinsp;+\u0026thinsp;50% VA and 25% RAP\u0026thinsp;+\u0026thinsp;75% VA exhibited crushing strengths comparable to VA. This observation aligns with findings by Lee and Kim (2017), who reported that blending RAP and VA in optimal proportions enhances interlocking and stability, yielding crushing values similar to VA. The angularity of RAP particles, shaped by crushing and milling processes, fosters improved interlocking in blends with VA, thereby enhancing crushing strength [76]. Studies by Kringos and Scarpas (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), suggest that older RAP can meet structural requirements when appropriately processed and incorporated into mix designs.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe chart 8 illustrates that the addition of more Virgin Aggregate (VA) with Reclaimed Asphalt Pavement (RAP) enhances the Aggregate Crushing Value (ACV), which means greater strength. At 100% RAP, the greater ACV (~\u0026thinsp;16%) implies less durable aggregate due to the oxidation of aged binder, causing the asphalt to become brittle and susceptible to crushing. With the addition of VA, ACV reduces, and the best mix is 50% RAP\u0026thinsp;+\u0026thinsp;50% VA, where the addition of fresh aggregate enhances interparticle bonding and load resistance. At 25% RAP\u0026thinsp;+\u0026thinsp;75% VA, an increase in ACV might be attributed to blending irregularities, decreased bitumen adhesion, or microstructural differences in aggregate composition. The trend indicates the importance of balanced RAP-VA ratios to achieve optimal mechanical performance while ensuring sustainability.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e4.3. Compaction tests\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eCompaction tests for Recycled Asphalt Pavement (RAP) are critical to determining its fitness for use in pavement construction. Compaction tests assist in the determination of RAP's density and void content, both of which play an important role in determining the structural strength, durability, and overall performance of the pavement. For the Standard Proctor Test (IS 2720 Part 7), a mold with a capacity of 1000 cm\u0026sup3; is used, having an internal diameter of 100 mm and a height of 127.3 mm. In this test, a hammer weighing 2.6 kg is dropped from a height of 310 mm to compact the material. For the Modified Proctor Test (IS 2720 Part 8), a larger mold with a capacity of 2250 cm\u0026sup3; is used, with an internal diameter of 150 mm and a height of 127.3 mm. This test uses a heavier hammer weighing 4.89 kg, which is dropped from a height of 450 mm to achieve higher compaction energy.\u003c/p\u003e\u003cp\u003eIn this research work, various blends of RAP and virgin aggregates (VA) were prepared in accordance with previously determined mix proportions. In order to improve the mechanical properties of the mixtures, stabilizing additives like cement, fly ash, and ground granulated blast furnace slag (GGBS) were added at percentages ranging from 3%, 5%, and 7%. These stabilizers have been commonly known to enhance the strength and stability of asphalt mixtures. For accurate and uniform results, both VA and RAP underwent the process of drying to remove any residual moisture for 48 hours prior to testing. Remove large aggregates (\u0026gt;\u0026thinsp;19 mm) to ensure consistency in compactionIn this study, various blends of RAP and VA were prepared based on previously selected proportions. Additives such as cement, fly ash, and GGBS were incorporated in varying percentages of 3%, 5%, and 7%. The use of these additives has been shown to enhance the mechanical properties of asphalt mixtures [43]. To ensure accurate results, both the VA and RAP were dried for 48 hours to eliminate moisture content. The specimens were then compacted using a hammer with a free fall distance of 457 mm and a weight of 4.5 kg.\u003c/p\u003e\u003cp\u003eThe results, depicted in Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e15\u003c/span\u003e, indicate a slight increase in density, while the OMC remained relatively consistent across the various blends. This consistency suggests that while the addition of materials may enhance the density of the mixtures, the moisture content at which optimal compaction occurs is stable. Such findings align with previous research indicating that the properties of asphalt mixtures can be significantly improved through careful optimization of mix designs (Sireesh 2016).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCompaction results of different mixes of RAP additives\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eADDITIVES %\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e100 RAP%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e75%RAP 25%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e50%RAP 50%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e25%RAP 75%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c11\" namest=\"c10\"\u003e\u003cp\u003e100 VA%\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOMC%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMDDGM/CC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOMC%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMDDGM/CC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eOMC%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMDDGM/CC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eOMC%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eMDDGM/CC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eOMC%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eMDDGM/CC\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.22\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e1.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe observed increase in maximum dry density (MDD) and optimum moisture content (OMC) in the 50% virgin aggregate (VA) blend with a 7% cement additive is attributed to the fundamental principles of soil stabilization, cement hydration, and particle packing. Cement acts as a binding agent, promoting hydration reactions that produce calcium silicate hydrates (C-S-H) and calcium aluminate hydrates (C-A-H), which enhance inter-particle bonding and reduce void spaces, leading to a denser and more compact structure.\u003c/p\u003e\u003cp\u003eCement addition also enhances RAP-VA granular interlock, improving compaction efficiency and mechanical stability. In addition, the optimum moisture content (OMC) of 9% allows for appropriate hydration to provide adequate lubrication among the particles during compaction and avoid unnecessary porosity. This enhanced densification increases load-bearing capacity, deformation resistance, and cracking resistance, rendering the RAP-cement mixture an ideal choice for pavement base and subbase. Moreover, cement stabilization with reduced permeability stops water intrusion, hence avoiding moisture-induced distress and ensuring longer pavement life. These reasons account for the enhanced mechanical properties, longevity, and sustainability of RAP-cement mixtures, which render them a successful option for road construction while fostering eco-friendly infrastructure development.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eMaximum Dry Density (MDD) and Optimum Moisture Content (OMC) of Virgin Aggregate (VA) mixed with Reclaimed Asphalt Pavement (RAP) are the important parameters for compaction properties, and incorporation of Fly Ash as a stabilizer has an important bearing on these properties. Figures\u0026nbsp;12, \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e13\u003c/span\u003e, and \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e14\u003c/span\u003e show the changes in MDD and OMC for varying RAP-VA mix proportions with 3%, 5%, and 7% Fly Ash, respectively. In general, when the RAP content is increased in the blend, MDD will decrease as a result of the lower unit weight of RAP than that of VA. Moreover, as the Fly Ash content increases from 3\u0026ndash;7%, MDD has a trend to decrease in some instances because of the reduced specific gravity and finer particle size of Fly Ash, which can influence the efficiency of compaction. Yet, there is a point of optimal Fly Ash content where its binding capability adds value without causing much density loss\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eFrom the Fig.\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e17\u003c/span\u003e shows the change in dry density with optimum moisture content (OMC) for various RAP-VA ratios stabilized with Ground Granulated Blast Furnace Slag (GGBS) at 3%, 5%, and 7%. The findings show that with increasing GGBS content, the dry density increases considerably at an optimal RAP-VA ratio. Maximum density is found at 50% RAP\u0026thinsp;+\u0026thinsp;50% VA, indicating good particle packing and pozzolanic reaction because of the availability of CaO, SiO₂, and Al₂O₃ in GGBS, which provides cementitious bonding. But beyond this proportion, at 75% VA, the density is reduced, probably because of improper blending of RAP and low cohesive properties. The OMC variation is due to the water absorption potential of RAP, where higher RAP content holds water, slowing down hydration reactions. The 5% and 7% GGBS peak densities show higher pozzolanic activity, but more than 7% GGBS can cause unreacted particles that decrease compactness. The results highlight the need for a balanced RAP-VA ratio with the optimal GGBS dose to ensure better strength and durability in pavement material.\u003c/p\u003e\u003cp\u003eReferring to the Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e to \u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e17\u003c/span\u003e, it is evident that the 50% virgin aggregates (VA) blend exhibited a higher maximum dry density (MDD) with an optimum moisture content (OMC) of 9% when combined with a 7% additive of cement. This finding aligns with previous studies indicating that the addition of cement improves the density and stability of asphalt mixtures. Compaction tests demonstrate that mixing RAP with cement enhances stability and reduces permeability, making it highly suitable for base and subbase layers in pavement construction.\u003c/p\u003e\u003cp\u003eThe optimized blend typically achieves a higher dry density and improved moisture retention, leading to stronger and more durable pavement layers. Additionally, incorporating cement significantly enhances the mechanical properties and load-bearing capacity of RAP, which in turn improves resistance to deformation and cracking. This is particularly important in ensuring the longevity of pavement structures, as noted by Rao et al. (2015). These benefits contribute to a longer pavement lifespan and reduced maintenance costs, establishing RAP-cement blends as a sustainable and efficient choice for road construction (Kandhal and mallick \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2001\u003c/span\u003e]. By optimizing the mix design and carefully selecting additives, the performance of RAP in pavement applications can be significantly improved, aligning with the goals of sustainable infrastructure development (Taha 2002).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003e4. 4. Unconfined compressive strength (UCS)\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe UCS test is used to determine the compressive strength of materials utilized in pavement. UCS is one of the most important mechanical properties of aggregates and is widely used in projects to evaluate the stability of pavements against loading [66]. Many authors have relied on the UCS test to determine the shear strength of pavements, with studies indicating that UCS is crucial for assessing the load-bearing capacity of pavement materials (Saride et al 2016). Data show that UCS can be improved by mixing cement, fly ash, and stabilizers such as GGBS. Cementitious materials like cement react with the fine particles of asphalt binder and aggregates present in RAP, facilitating pozzolanic reactions that form additional cementitious compounds, thereby enhancing the strength and durability of the blend. RAP contains fine particles that can act as fillers within the cement matrix, reducing the overall porosity of the material and enhancing its strength by filling the voids between cement grains The addition of cement improves the resistance of the pavement to rutting, which is the permanent deformation caused by repeated traffic loading. Cement helps to stiffen the RAP mixture, thereby mitigating rutting and improving the long-term performance of the pavement, as noted by (Dong Q, Huang B \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The addition of fly ash significantly increased the UCS of 100% RAP mixed with fly ash blends(Saride et al \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The incorporation of fly ash alongside RAP assists in filling the voids between larger aggregates, reducing porosity and increasing the density of the pavement. This filler effect contributes to improved mechanical properties, including increased UCS, as emphasized by Jayakody et al. (2017).\u003c/p\u003e\u003cp\u003eSince VA is better integrated with RAP, the UCS value increases as VA content increases [74]. Samples of 100 mm in length and 200 mm in height were prepared from each combination. To determine the MDD and OMC, casting samples were tested according to IRC Specification: 37-2012, which recommends a minimum pressure of 4.5 MPa at 28 days of curing. Figures\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e18\u003c/span\u003e, \u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e19\u003c/span\u003e, and \u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e20\u003c/span\u003e show the compressive strength of RAP\u0026thinsp;+\u0026thinsp;VA with the addition of different proportions of cement, fly ash, and GGBS. The UCS results revealed that 50% RAP\u0026thinsp;+\u0026thinsp;50% VA mixes showed higher strength than 100% RAP.\u003c/p\u003e\u003cp\u003eIn general, RAP exhibits a lower UCS compared to conventional asphalt mixtures due to the aging of the asphalt binder, and it may contain moisture and contaminants in the recycled material (Vidal 2013). However, advances in technology and the inclusion of additional materials can enhance the strength of RAP, enabling its effective use in pavement applications. Consequently, RAP can be blended with additives like cement, fly ash, and GGBS. The adopted mix proportions and the strength evaluations of these mixes are reported in Table \u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e5\u003c/span\u003e to \u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDifferent proportions of RAP with VA for UCS test\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eADDITIVES %\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100 RAP%\u003c/p\u003e\u003cp\u003eUCS (N/ MM2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e75%RAP 25%VA\u003c/p\u003e\u003cp\u003eUCS (N/ MM2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e50%RAP 50%VA\u003c/p\u003e\u003cp\u003eUCS (N/ MM2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25%RAP 75%VA\u003c/p\u003e\u003cp\u003eUCS (N/ MM2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100 VA%\u003c/p\u003e\u003cp\u003eUCS (N/ MM2)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e3.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4. 85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.66\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e3.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.66\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.82\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe Table \u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e5\u003c/span\u003e presents the Unconfined Compressive Strength (UCS) values in N/mm\u0026sup2; for different compositions of Reclaimed Asphalt Pavement (RAP) and Virgin Aggregate (VA) mixtures, stabilized with varying percentages of Cement, Fly Ash (FA), and Ground Granulated Blast Furnace Slag (GGBS). The tests reveal that the strength of the mixes depends on the stabilizer type and percent, as well as the percentage of RAP and VA used in the mix. Cement-stabilized blends typically have the highest UCS values among various RAP-VA compositions, with cement content increasing strength. The highest UCS of 4.98 N/mm\u0026sup2; is attained by the 50% RAP \u0026ndash; 50% VA mix with 7% cement among all mixes, indicating a balanced mixture between RAP and VA when cement is employed as a stabilizer. The UCS values for 100% RAP are lower than those for mixes with VA, indicating the necessity of mixing RAP with virgin aggregates to achieve structural strength. Fly Ash-stabilized mixtures exhibit comparatively lower UCS values than cement-stabilized ones. But a rising proportion of FA leads to an improvement in strength, though not very high. The maximum UCS (4.94 N/mm\u0026sup2;) for FA-stabilized mixtures is seen in the 50% RAP \u0026ndash; 50% VA mixture with 7% FA, which means FA can prove to be a good stabilizer when utilized in suitable proportions. GGBS-stabilized mixtures typically have lower UCS values than cement and FA. The strength of GGBS-stabilized mixtures increases with increasing VA content, and the maximum UCS of 4.78 N/mm\u0026sup2; was achieved for the 50% RAP \u0026ndash; 50% VA mix containing 7% GGBS. While GGBS enhances strength, its effect seems less pronounced than that of cement. In general, the results indicate that the addition of a balanced ratio of RAP and VA improves the mechanical performance of the mixture, with the 50% RAP \u0026ndash; 50% VA mixture producing the highest UCS in all the stabilizers. Cement is found to be the best stabilizer, followed by FA and GGBS. The findings emphasize the possibility of utilizing RAP with suitable stabilizers to obtain a sustainable and structurally adequate pavement material.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003e4.5 Indirect tensile strength (Moisture Sensitivity test)\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eIndirect Tensile Strength (ITS) is a crucial test for evaluating the tensile strength and moisture susceptibility of bituminous mixes, including Reclaimed Asphalt Pavement (RAP)-based mixes. It helps in assessing cracking resistance under repeated traffic loads. The Indirect Tensile Strength (ITS) of Reclaimed Asphalt Pavement (RAP) can be significantly enhanced through the incorporation of stabilizing agents such as cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) by ASTM D6931 or AASHTO T 283. Studies by Taha et al. (2002) and Modarres \u0026amp; Ayar (2014) have shown that cement improves the mechanical properties of RAP by acting as a hydraulic binder, increasing stiffness and strength. Similarly, research by Kim et al. (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) highlights the role of fly ash, a pozzolanic material, in long-term strength gain, as it reacts with available lime to form additional binding compounds, thereby improving cohesion. The combined effect of these additives results in an increased ITS, as observed in the studies by Mohammadinia et al. (2017), indicating better resistance to tensile cracking and improved load-bearing capacity. However, as noted by Wen et al. (2013), the effectiveness of these stabilizers depends on several factors, including the percentage of additives, curing period, RAP gradation, and moisture content. Proper optimization of these parameters ensures a balance between flexibility and strength, making RAP a viable and sustainable material for pavement rehabilitation and construction. Each of these RAP:VA blends was further stabilized with cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) at varying percentages of 3%, 5%, and 7% by weight of the total mixture. The IDT strength test was used to determine tensile strength and strain of the mixture specimens compacted to 4\u0026thinsp;\u0026plusmn;\u0026thinsp;1% air voids. Cylindrical specimens with 100 mm in diameter and 63.5mm in height were monotonically loaded to failure along the vertical diametric axis at the constant rate of 76.2 mm/min.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIndirect tensile strength of RAP\u0026thinsp;+\u0026thinsp;VA mixes with various proportions\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdditives %\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e100 RAP%\u003c/p\u003e\u003cp\u003eITS\u003c/p\u003e\u003cp\u003e(N/ mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e75%RAP 25%VA\u003c/p\u003e\u003cp\u003eITS\u003c/p\u003e\u003cp\u003e(N/ mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e50%RAP 50%VA\u003c/p\u003e\u003cp\u003eITS\u003c/p\u003e\u003cp\u003e(N/ mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25%RAP 75%VA\u003c/p\u003e\u003cp\u003eITS\u003c/p\u003e\u003cp\u003e(N/ mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e100 VA%\u003c/p\u003e\u003cp\u003eITS\u003c/p\u003e\u003cp\u003e(N/ mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eRefer table: 6 Indirect Tensile Strength (ITS) of Reclaimed Asphalt Pavement (RAP) and Virgin Aggregate (VA) blends largely depends on the type and quantity of additives used for stabilization. The values given indicate differences in ITS values among different RAP-VA mixes stabilized with different percentages of Cement, Fly Ash (FA), and Ground Granulated Blast Furnace Slag (GGBS). With the increasing proportion of VA in the blend, ITS values tend to increase, reflecting better strength resulting from the enhanced interlocking and compaction behavior of VA over RAP\u003c/p\u003e\u003cp\u003eRefer Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e21\u003c/span\u003e to 23 among the stabilizers, cement has the highest ITS values for all RAP-VA ratios, with a significant increase as the cement content increases from 3\u0026ndash;7%. At 7% cement, the maximum ITS value of 2.85 N/mm\u0026sup2; is recorded for 100% VA, and even the mixtures with higher RAP content (100% RAP and 75% RAP-25% VA) exhibit significant tensile strength improvements. This is due to the fact that cement has better binding qualities, which increase the cohesion and structural strength of the mix. Fly Ash also enhances ITS, but its effect is comparatively moderate in nature relative to cement. At 7% FA, ITS values vary from 1.75 N/mm\u0026sup2; for 100% RAP to 2.25 N/mm\u0026sup2; for 100% VA, indicating that FA helps in strength gain but does not offer as much binding capacity as cement. Nevertheless, its capacity to enhance workability and minimize moisture susceptibility makes it a good substitute for RAP stabilization. GGBS follows a similar pattern but with lower ITS values than cement and FA. ITS values are higher with greater VA content, but even at 7% GGBS, the maximum strength achieved is 2.15 N/mm\u0026sup2; for 100% VA. This suggests that although GGBS is strength-enhancing, its stabilizing effect is relatively lower than cement and FA in tensile resistance. In general, the choice of stabilizers is a function of strength requirements and material availability. Cement yields the highest strength increments and is the first choice for applications requiring high durability. Fly Ash gives balanced improvement in strength and workability, while GGBS, while less efficient in raising ITS, remains a suitable stabilizer in RAP-VA mixtures. These results emphasize the need to choose the right additives in accordance with project needs to maximize pavement performance.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003e4.5. California bearing ratio\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe California Bearing Ratio (CBR) test is crucial for predicting the durability and mechanical properties of compacted materials. It serves as a key specification for defining the bearing capacity of pavement under traffic loading, ultimately influencing pavement thickness. Laboratory studies consistently demonstrate that CBR values increase with a higher percentage of VA) while decreasing with an increased presence of RAP in the mix [75]. To enhance the strength of the pavement base layer, additives such as Portland cement (PC), fly ash, and ground granulated blast furnace slag (GGBS) can be effectively incorporated with RAP. Testing the load-bearing capacity of 100% RAP combined with 1%, 2%, and 3% cement revealed that a mix of 50% RAP and 50% limerock-based asphalt emulsion achieved CBR values exceeding 100 [15]. The combination of RAP with recycled coarse aggregates (RCA) has also shown promising results, with studies indicating that RCA enhances load-bearing capacity and durability(Seferoǧlu 2018). According to recommendations from the Queensland Department of Transport and Highways (QDTMR), a high RAP content of 20% is feasible for pavement layers. Moreover, crushed clay bricks combined with RCA have demonstrated sufficient strength for use as unbound subbase material (Poon \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). The improvement of mechanical properties in RCA and limestone aggregate (LSA) enhances their suitability for road subbases or bases. CBR values tend to increase with a higher RCA content and a lower RAP percentage, indicating RCA's superior quality compared to RAP. Optimal CBR values of approximately 78% have been achieved with a mix containing a maximum of 15% RAP. However, higher RAP content results in decreased CBR values, primarily due to the bitumen-coated aggregates sliding over each other under load. The best pavement performance is generally observed with a 50/50 mixture of RAP and RCA [10]. CBR tests conducted on samples with varying RAP and VA contents have shown that 100% RAP does not provide acceptable base course quality. As RAP content increases, CBR values fall below acceptable levels, leading to a recommendation of limiting RAP to 50% when combined with 50% VA. The reduced strength is attributed to the lower viscosity of the bituminous binder, which causes increased deformation under summer conditions and traffic loads. Specifically, when RAP content rises from 0\u0026ndash;25% and from 50\u0026ndash;75%, CBR results decrease by 50\u0026ndash;75% and 75\u0026ndash;100%, respectively. Notably, when RAP is blended with an optimum of 7% cement, higher CBR values are observed. Furthermore, cement-treated RAP combined with VA outperforms mixes treated with fly ash and GGBS, reinforcing the importance of optimizing blend ratios for enhanced pavement performance.\u003c/p\u003e\u003cp\u003eFrom the Fig.\u0026nbsp;24\u0026ndash;26 clearly shows that Variation in CBR with different blends of RAP with varying percentage of cement, fly ash and GGBS. From the test result a balanced mix\u0026mdash;typically a 50/50 ratio of Reclaimed Asphalt Pavement (RAP) optimizes California Bearing Ratio (CBR), often exceeding 100, demonstrating sufficient durability and load-bearing capacity. A recent study by Mishra et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) has confirmed that this balanced RAP ratio provides an ideal compromise between sustainability and mechanical performance. Cement-treated RAP and virgin aggregate (VA) blends exhibit the highest CBR values, outperforming those treated with fly ash or Ground Granulated Blast Furnace Slag (GGBS), highlighting the need for optimized blend ratios to enhance pavement performance. For practical applications, limiting RAP to around 50% and incorporating strength-enhancing additives like cement offers a promising approach to maintaining pavement integrity under traffic loading (Deng 2021). When cement is introduced into a RAP mix, a pozzolanic reaction occurs between the cement and the finer particles in the RAP. Recent findings by Zhao and Zhang (2012) indicate that cement hydration products improve cohesion in RAP mixes. Cement hydrates react with the bituminous coating on RAP aggregates, partially stripping the bitumen and forming a more cohesive matrix, resulting in improved bonding and a stiffer, more durable layer. This process enhances the structural integrity of the RAP mix by reducing the inherent weakness associated with bitumen-coated surfaces that can otherwise slip under load. The chemical bonds formed between the cement and RAP particles offset the otherwise low CBR values typically seen in high RAP content mixtures. While RAP is a cost-effective and sustainable material, limiting its percentage in a pavement mix to around 50% is crucial to maintaining optimal performance. As demonstrated by (Wang et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), high RAP content can lead to an excess of bituminous material, which may reduce friction between particles and compromise strength under load. Refer Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e19\u003c/span\u003e to \u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e21\u003c/span\u003ea balanced 50/50 RAP-VA blend maximizes load-bearing capacity while preserving pavement integrity, as the fresh aggregates provide structural support that counteracts RAP\u0026rsquo;s reduced frictional resistance. This balance also helps to avoid excessive brittleness or susceptibility to fatigue, which is more likely when RAP content exceeds 50%, especially under high traffic loads. The results of CBR revealed that, for all additives, 50% RAP with 50% VA blends have given higher CBR, with increase in RAP proportion, CBR decreases due to reduced stiffness and gradation change in the mix.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\u003ch2\u003e4.6. Marshall stability test\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe Marshall Stability test is a crucial laboratory procedure used to assess the performance and durability of asphalt mixtures, including those incorporating reclaimed materials. This test measures an asphalt mixture's resistance to deformation and failure under standardized conditions, ensuring that the mix meets specified performance and durability standards (ASTM D1559). According to Prajnas and Ilyas Anjum (2014), the test evaluates both stability and flowability, making it valuable for assessing RAP-based mixes. Several studies have indicated that the incorporation of cement, fly ash, and Ground Granulated Blast Furnace Slag (GGBS) into Reclaimed Asphalt Pavement (RAP) significantly improves both the mechanical properties and the durability of RAP mixtures. As noted by Zhao et al. (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), cement and fly ash increase stability and stiffness through enhanced binder-aggregate bonding, while GGBS provides additional strength and moisture resistance. The synergy of these additives addresses the aged binder's rigidity in RAP, resulting in a more workable and resilient mix (Zhao et al \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Research highlights that optimal combinations of RAP with cement, fly ash, and GGBS achieve stability values comparable to or exceeding traditional asphalt mixtures, making them suitable for high-traffic applications. This approach supports sustainable pavement design by effectively recycling materials while preserving structural integrity and longevity. The Marshall Stability Test is primarily utilized to measure the deformation properties and strength of asphalt mixtures but is not a stiffness analysis in direct terms. Rather, it determines the stability and flow, which indirectly reflect the mix's resistance to cracking and rutting. Whereas the test gives insight into the total load-bearing capacity, it does not uniquely measure stiffness as tests such as the Dynamic Modulus or Indirect Tensile Stiffness Modulus (ITSM) Test are better applicable to stiffness analysis. Increased Marshall stability value can, however, be related to higher mix stiffness, but this is not enough for complete stiffness characterization, particularly for RAP mixes.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eNomenclature followed for different proportions of RAP with VA for Marshall stability test\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"11\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eADDITIVES %\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e100 RAP%\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003e75%RAP 25%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e50%RAP 50%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e\u003cp\u003e25%RAP 75%VA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c11\" namest=\"c10\"\u003e\u003cp\u003e100 VA%\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStability (kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFlow (mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStability (kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFlow(mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eStability\u003c/p\u003e\u003cp\u003e(kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eFlow (mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eStability(kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eFlow\u003c/p\u003e\u003cp\u003e(mm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eStability\u003c/p\u003e\u003cp\u003e(kN)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eFlow\u003c/p\u003e\u003cp\u003e(mm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e13.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e13.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.05\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e13.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e13.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% Cement\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e15.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e17.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e3.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e17.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e14.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e14.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e14.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e14.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e15.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e15.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e15..02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% FA\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e15.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e15.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e15.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e15.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e15.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.76\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e3% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e11.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e11.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e11.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e11.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e5% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e12.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e12.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e7% GGBS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e14.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e13.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e15.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e15.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e2.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e15.09\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e2.65\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eA mixture of 50% Reclaimed Asphalt Pavement (RAP) and 50% virgin aggregate (VA) stabilized with 7% cement gains strength due to enhanced bonding and rigidity. Cement binds the RAP and VA particles, creating a dense, cohesive matrix that resists deformation(Ranjitham Mariyappan et al \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e].This reduces voids, improves load distribution, and enhances moisture resistance, resulting in greater durability. The cement also stabilizes the aged binder in RAP, contributing to stronger aggregate-binder interaction. Together, these factors provide a high-strength, long-lasting pavement mix. In the Marshall stability test, the 50% RAP and 50% VA mixture stabilized with 7% cement demonstrates high stability due to the improved bonding, rigidity, and reduced voids provided by cement. The dense, cohesive matrix enhances load-bearing capacity, distributes stresses effectively, and improves moisture resistance, leading to greater durability. The cement's stabilization of the aged RAP binder strengthens the aggregate-binder interaction, contributing to a high-strength, resilient pavement mix well-suited for long-term performance under traffic loading.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec23\" class=\"Section2\"\u003e\u003ch2\u003e\u003cb\u003e4.7 Scope of cost-benefit analysis\u003c/b\u003e\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe essential reuse of discarded waste materials for environment-friendly solutions in pavement protection, conservation, and reconstruction has been extensively appraised in recent years (Li et al 2021). Thousands of tons of waste are produced worldwide every year, which can be reprocessed and reused on roads, safeguarding the environment by reducing waste and saving materials (Tighe et al 2015). The analysis of low energy consumption in transportation is mainly divided into two ways: (1) reducing the cost of asphalt pavement and reducing the cost of materials(Brown 2009). In this study, various composites were produced, but HMA performance was not considered. Therefore, the main purpose of this study is to follow the second method, material cost analysis, while exploring other methods. Loading, milling, placement, and contract work are not included in the estimated cost because these activities are the same for virgin materials RAP (Recycled Asphalt Pavement) is an admirable material used in highway construction(Li et al 2021). Using RAP is a constructive strategy because recycled materials reduce the need for virgin materials, thus making road construction more sustainable. Additionally, incorporating RAP into the asphalt mixture can recover pavement performance and durability, thereby reducing maintenance and repair costs over the life of the pavement. From an environmental perspective, the use of RAP reduces the demand on natural resources and minimizes landfill waste [46].\u003c/p\u003e\u003cp\u003eIn general, cost savings of 20\u0026ndash;50% can be achieved using RAP compared to conventional asphalt mixtures made from virgin materials (Chen 2014). These savings result from reduced equipment costs, transportation costs, and maintenance costs over the life of the coating (Park et al \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Overall, the cost-benefit analysis of recycled asphalt pavement demonstrates its economic and environmental benefits, making it a sustainable choice for road construction and rehabilitation projects (Sharma et al 2018). The minimization of landfill waste from the utilization of Reclaimed Asphalt Pavement (RAP) is motivated by numerous factors. RAP facilitates recycling of aged asphalt, reducing enormously the quantity of construction waste to be sent to landfills. Through the application of RAP in new pavements, utilization of virgin aggregates is reduced, thus preserving nature and minimizing material extraction's adverse effects on the environment. Apart from that, reuse of RAP decreases energy usage in the production of asphalt, thus saving costs in road construction. Circular economy principles are enhanced by sustainable pavement practices, which ensure material reuse instead of disposal. Additionally, use of RAP is in line with environmental policy and regulations as well as waste management policies, and it promotes environmentally friendly construction practices.\u003c/p\u003e\u003cp\u003eRAP is an essential tool for achieving sustainable construction methodologies in road infrastructure through minimizing dependence on virgin resources and environmental pollution. Through the use of RAP in fresh asphalt mix, the use of natural aggregates is greatly reduced, thus preserving non-renewable resources. The recycling of asphalt pavement also prevents construction and demolition waste, whereby huge amounts of material are not sent to landfill. In addition, RAP helps improve energy efficiency by reducing the demand for significant material processing and lowering emissions from asphalt production. The cost savings of RAP also help improve sustainability since it reduces material and transport costs while conserving pavement performance. Further, RAP use helps promote circular economy ideals by establishing a closed-loop process in which materials are recycled repeatedly and conform to environmental controls and green infrastructure practices. By incorporating RAP into road building, planners and engineers achieve long-term sustainability as well as enhancing the resilience and durability of transportation infrastructure.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec24\" class=\"Section2\"\u003e\u003ch2\u003e4.8 Life Cycle Analysis (LCA) of Reclaimed Asphalt Pavement (RAP)\u003c/h2\u003e\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eRAP Life Cycle Analysis (LCA) evaluates its entire life cycle environmental impacts from extraction to recycling or disposal. RAP normally originates from the milling or asphalt stripping from previously laid pavements as part of resurfacing or reconstruction jobs. This method minimizes the demand for virgin raw material to a considerable extent, since it facilitates reusing the top asphalt layer and thus lessens the environmental load of virgin material extraction (Zhang et al., 2020). Through the utilization of RAP, the demand for new aggregates as well as bitumen is reduced, according to (McDaniel et al. 2011), making it a green solution for conventional construction material.\u003c/p\u003e\u003cp\u003eAfter RAP is gathered, it is taken to processing plants or to building sites, and transportation effects such as fuel use and GHG emissions are factored in. The magnitude of these effects is a function of factors like distance covered and type of transport utilized (i.e., truck or train. During the processing phase, RAP is generally screened, crushed, and heated prior to being utilized in new asphalt mixtures. Even though energy is needed for such processes, research indicates that the energy consumption of RAP is much lower than that of virgin material production (Li et al., 2021). Additionally, the emissions produced during the processing of RAP are much lower than those produced in fresh asphalt production.\u003c/p\u003e\u003cp\u003eWith the use of RAP in fresh asphalt mix, it not only lowers the requirements for virgin resources but also maximizes the sustainability of pavement making through minimizing wastes and saving resources (Zhang et al., 2020). Studies conducted by Lippiatt et al. (2019) illustrate that recycling RAP can help reduce material cost as well as carbon emissions during asphalt production. At the end of its life cycle, RAP is still a useful material for future recycling in paving projects, encouraging a circular economy. As noted by Giani et al. (2020), repeated recycling of RAP through several life cycles can effectively minimize environmental effects, as well as natural resource consumption.\u003c/p\u003e\u003cp\u003eOverall, utilization of RAP in roadwork provides a number of environmental benefits, such as minimizing waste generation, saving natural resources, and conserving energy, hence the integral part of sustainable infrastructure planning. By mitigating the dependence on virgin resources and advancing towards a circular economy, RAP is an essential component in bringing down the environmental footprint of construction.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"6. CONCLUSION","content":"\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eRAP materials exhibited coarser gradation compared to virgin aggregates (VA), affecting compaction and interlocking properties. Proper blending with VA improved particle packing, reducing voids and enhancing structural integrity.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eRAP mixes needed more energy to mix because of hardened binder characteristics. Mixing with VA and stabilizers enhanced workability of the mix, facilitating uniform binder and fines distribution.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe 50% RAP\u0026ndash;50% VA blend with 7% cement had the greatest Maximum Dry Density (MDD) and optimum Optimum Moisture Content (OMC) and had superior compaction as well as better structural stability and was appropriate for road base and subbase constructions.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eUnconfined Compressive Strength (UCS) results established that the cement-stabilized RAP-VA combinations had the best strength with an optimum UCS value of 4.98 N/mm\u0026sup2; and greatly enhanced resistance to load over unstabilized RAP.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe California Bearing Ratio (CBR) test showed that the RAP-VA mix stabilized with cement had the greatest CBR value of 108%, which represents improved load-carrying capacity for use in high-traffic pavements and environmentally friendly road construction.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eIndirect Tensile Strength (ITS) tests showed that tensile strength was greatly enhanced by cement stabilization with a peak ITS of 2.75 N/mm\u0026sup2;, providing enhanced crack resistance. FA-treated mixtures recorded 1.97 N/mm\u0026sup2;, and GGBS-treated mixtures recorded 1.45 N/mm\u0026sup2;, indicating the efficacy of cement as a stabilizer.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eMarshall Stability test upheld that the deformation resistance of cement-stabilized RAP-VA mix was superior, which registered a peak stability of 15.6 kN compared to FA-stabilized (14.8 kN) and GGBS-stabilized (14.2 kN) mixes and thus proves best suited for high-performance asphalt pavement.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAnalysis through X-ray Fluorescence (XRF) revealed that the major oxides present in RAP include SiO₂, Al₂O₃, CaO, and Fe₂O₃ with more silica being more beneficial towards improving aggregate durability and mechanical strength.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eFourier Transform Infrared Spectroscopy (FT-IR) analysis identified oxidation markers like carbonyl (C\u0026thinsp;=\u0026thinsp;O) at ~\u0026thinsp;1700 cm⁻\u0026sup1;, sulfoxide (S\u0026thinsp;=\u0026thinsp;O) at ~\u0026thinsp;1030 cm⁻\u0026sup1;, and hydroxyl (-OH) at ~\u0026thinsp;3400 cm⁻\u0026sup1;, validating binder aging and the need for rejuvenators to rehabilitate asphalt characteristics towards long-term pavement sustainability.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eEnvironmental and economic benefits were evident since RAP use drastically cuts virgin aggregate consumption, reduces construction costs, and facilitates sustainable pavement construction in harmony with circular economy.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe study demonstrates that cement-stabilized RAP-VA mixes offer superior strength, improved durability, and greater deformation resistance, positioning them as a feasible, cost-efficient, and sustainable option for contemporary road infrastructure.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eRAP use lessens the reliance on virgin aggregates, decreases asphalt binder usage, and reduces construction waste, promoting sustainable and environmentally friendly practices in pavement construction.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eBased on the test results, when the RAP percentage exceeds 50%, the strength decreases due to limited binder availability, increased material stiffness, and insufficient blending with virgin aggregates, resulting in reduced structural integrity.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e7. FUTURE STUDY\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eInnovative approaches, such as bio-based rejuvenators and chemical additives, can enhance the flexibility and durability of RAP mixes while minimizing environmental impact.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eFurther studies should evaluate the long-term environmental benefits of high RAP content in asphalt mixes, including reduced carbon emissions, lower energy consumption, and waste minimization. Additionally, exploring the integration of other recycled materials, such as waste plastics or industrial by-products, can enhance sustainability.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe use of rejuvenators and softening agents in RAP can significantly improve binder flexibility and reduce brittleness. Research should focus on optimizing dosages and formulations to enhance resistance to moisture damage, fatigue cracking, and oxidation.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe incorporation of fibers in high-RAP asphalt mixes presents a promising avenue to improve durability, stability, and cracking resistance. Future studies should explore various fiber types, such as cellulose, polymer, or steel fibers, to determine their optimum contribution to mix performance.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThe synergistic effects of additives, such as polymer modifiers and supplementary cementitious materials, require further investigation. These additives can enhance rutting resistance, moisture susceptibility, and overall structural integrity of RAP-based pavement layers.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eWhile laboratory studies provide valuable insights, long-term field performance evaluations are necessary to validate RAP stabilization techniques. Research should focus on real-world pavement monitoring, assessing factors like traffic load response, climate effects, and maintenance needs for high-RAP pavements.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the infrastructural facilities and manpower resources provided by the Bannari amman institute of technology, Sathy, Erode, Tamilnadu, India for the execution of the project work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors did not receive any specific funding for this work.\u003c/p\u003e\n\u003cp\u003eOr:\u003c/p\u003e\n\u003cp\u003eNo funds, grants, or other support was received for conducting this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRanjitham conducted the research and wrote the manuscript. Jeyapriya and Soundara critically reviewed and revised the content. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis article does not contain any studies with human participants or animals performed by any of the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors give consent for the publication that the research details in the paper are to be published in this journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that guide the results of this research will be available openly.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbraham SM, Ransinchung GDRN (2018) Strength and permeation characteristics of cement mortar with Reclaimed Asphalt Pavement Aggregates. 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Hern\u0026aacute;ndez-Vidal G, \u0026quot;Effect of asphalt binder grade on the performance of asphalt mixtures containing reclaimed asphalt pavement (RAP)\u0026quot;, \u003cem\u003eConstruction and Building Materials\u003c/em\u003e, v.204, pp.244-252, 2019 https://doi.org/10.1016/j.conbuildmat.2019.01.172.\u003c/li\u003e\n\u003cli\u003eGiani M I, Dotelli G, Brandini N and Zampori L, \u0026ldquo;Comparative life cycle assessment of asphalt pavements using reclaimed asphalt, warm mix technology and cold in place recycling\u0026rdquo;, \u003cem\u003eResources, Conservation and Recycling\u003c/em\u003e, v.104, pp.224-238, 2015.\u003c/li\u003e\n\u003cli\u003eHansen K R, Copeland A, \u0026ldquo;Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2016\u0026rdquo;, \u003cem\u003eInformation Series 138, National Asphalt Pavement Association, Lanham, MD\u003c/em\u003e, 2017.\u003c/li\u003e\n\u003cli\u003eHuang B, LI G, Vukosavljevic D, Shu X, Egan B, \u0026quot;Laboratory Investigation of Mixing Hot-Mix Asphalt with Reclaimed Asphalt Pavement\u0026quot;, \u003cem\u003eTransportation Research Record: Journal of the Transportation Research Board\u003c/em\u003e. 1929, pp. 37-45, 2005, DOI: 10.1177/0361198105192900105.\u003c/li\u003e\n\u003cli\u003eIndian Roads Congress, \u0026quot;IRC:37-2018 Guidelines for the Design of Flexible Pavements\u0026quot;, \u003cem\u003eNew Delhi, India: Indian Roads Congress\u003c/em\u003e, 2018.\u003c/li\u003e\n\u003cli\u003eIndian Roads Congress, \u0026quot;IRC 015: Guidelines for the Design of Sub-Grade for Pavements\u0026quot;, \u003cem\u003eNew Delhi, India: Indian Roads Congress\u003c/em\u003e, 2011.\u003c/li\u003e\n\u003cli\u003eIndian Roads Congress, \u0026ldquo;Guidelines for the Design of Flexible Pavements (IRC: 37-2012)\u0026rdquo;, \u003cem\u003eNew Delhi: Indian Roads Congress\u003c/em\u003e, 2012.\u003c/li\u003e\n\u003cli\u003eIS: 2386 (Part II) - 1963: Methods of Test for Aggregates for Concrete \u0026ndash; Estimation of Deleterious Materials and Organic Impurities - Bureau of Indian Standards, New Delhi, India.\u003c/li\u003e\n\u003cli\u003eIS: 2386 (Part III) - 1963: Methods of Test for Aggregates for Concrete \u0026ndash; Specific Gravity, Density, Voids, Absorption, and Bulking - Bureau of Indian Standards, New Delhi, India.\u003c/li\u003e\n\u003cli\u003eIS: 2386 (Part IV) - 1963: Methods of Test for Aggregates for Concrete \u0026ndash; Mechanical Properties - - Bureau of Indian Standards, New Delhi, India.\u003c/li\u003e\n\u003cli\u003eIS: 2386 (Part V) - 1963: Methods of Test for Aggregates for Concrete \u0026ndash; Soundness - Bureau of Indian Standards, New Delhi, India.\u003c/li\u003e\n\u003cli\u003eIS: 2386 (Part VI) - 1963: Methods of Test for Aggregates for Concrete \u0026ndash; Measuring Mortar Making Properties of Fine Aggregate -- Bureau of Indian Standards, New Delhi, India.\u003c/li\u003e\n\u003cli\u003eJayakody S, Gallage C, Ramanujam J, \u0026ldquo;Effects of reclaimed asphalt materials on geotechnical characteristics of recycled concrete aggregates as a pavement material\u0026rdquo;, \u003cem\u003eRoad Materials and Pavement Design, \u003c/em\u003ev.20, n.4, pp.754\u0026ndash;772, 2019, https://doi.org/10.1080/14680629.\u003c/li\u003e\n\u003cli\u003eKandhal PS \u0026amp; 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A review\u0026quot;, \u003cem\u003eMaterials Today: Proceedings\u003c/em\u003e, v.46, pp.6558-6566, 2022, https://doi.org/10.1016/j.matpr.2021.04.057.\u003c/li\u003e\n\u003cli\u003eRoberts FL, Kandhal PS, Brown ER, Lee DY, Kennedy TW, \u0026ldquo;Hot Mix Asphalt Materials, Mixture Design and Construction, 2nd Edition\u0026rdquo;, \u003cem\u003eNational Asphalt Pavement Association Research and Education Foundation\u003c/em\u003e, 1996.\u003c/li\u003e\n\u003cli\u003eSaride S, Avirneni D, Javvadi SCP, Puppala AJ, Hoyos LR, \u0026ldquo;Evaluation of Fly ash Treated Reclaimed Asphalt Pavement for Base/Subbase Applications\u0026rdquo;, \u003cem\u003eIndian Geotechnical Journal\u003c/em\u003e, v.45, n.4, pp.401\u0026ndash;411, 2015, https://doi.org/10.1007/s40098-014-0137-z.\u003c/li\u003e\n\u003cli\u003eSaride S, Avirneni D, Javvadi SCP, \u0026ldquo;Utilization of Reclaimed Asphalt Pavements in Indian Low-Volume Roads\u0026rdquo;, \u003cem\u003eJournal of Materials in Civil Engineering,\u003c/em\u003e v.28, n.2, art.04015107, 2016(b), https://doi.org/10.1061/(asce)mt.1943-5533.0001374.\u003c/li\u003e\n\u003cli\u003eSaride S, Avirneni D, Javvadi SCP, \u0026ldquo;Utilization of Reclaimed Asphalt Pavements in Indian Low-Volume Roads\u0026rdquo;, \u003cem\u003eJournal of Materials in Civil Engineering,\u003c/em\u003e v.28, n.2, art04015107, 2016(a), https://doi.org/10.1061/(asce)mt.1943-5533.0001374.\u003c/li\u003e\n\u003cli\u003eSeferoǧlu AG, Seferoǧlu MT, Akpinar MV, \u0026ldquo;Investigation of the Effect of Recycled Asphalt Pavement Material on Permeability and Bearing Capacity in the Base Layer\u0026rdquo;, \u003cem\u003eAdvances in Civil Engineering,\u003c/em\u003e 2018, https://doi.org/10.1155/2018/2860213\u003c/li\u003e\n\u003cli\u003eSireesh Saride, Deepti Avirneni, Subrahmanyam Challapalli, \u0026ldquo;Micro-mechanical interaction of activated fly ash mortar and reclaimed asphalt pavement materials\u0026rdquo;, \u003cem\u003eConstruction and Building Materials, \u003c/em\u003ev.123, pp.424\u0026ndash;435, 2016, https://doi.org/10.1016/j.conbuildmat.2016.07.016.\u003c/li\u003e\n\u003cli\u003eShirodkar P, Meagher W, Arambula E, Epps Martin A, Estakhri C, \u0026quot;Investigation of Properties of Plant-Produced RAP Mixtures\u0026quot;, \u003cem\u003eJournal of the Association of Asphalt Paving Technologists\u003c/em\u003e,v. 80, pp. 527-548, 2011.\u003c/li\u003e\n\u003cli\u003eTaha R, Ali G, Basma A, Al-Turk O, \u0026ldquo;Evaluation of Reclaimed Asphalt Pavement Aggregate in Road Bases and Subbases\u0026rdquo;, \u003cem\u003eTransportation Research Record\u003c/em\u003e, v.1652, n.1, pp.264\u0026ndash;269, 1999.\u003c/li\u003e\n\u003cli\u003eTang S, Zhang Y \u0026amp; 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Chen Y, \u0026ldquo;Mechanical performance of high RAP content mixtures in pavement base layers\u0026rdquo;, \u003cem\u003eInternational Journal of Pavement Engineering\u003c/em\u003e, v.24, n.5, pp.623-631, 2023.\u003c/li\u003e\n\u003cli\u003eWest R, Copeland A \u0026amp; King G, \u0026quot;Asphalt Binder Aging and Its Implications on Recycled Material Usage and Performance\u0026quot;, \u003cem\u003eTransportation Research Record: Journal of the Transportation Research Board\u003c/em\u003e, v.2672, n.28, pp.1-9, 2018, https://doi.org/10.1177/0361198118758699.\u003c/li\u003e\n\u003cli\u003eZhao Y, Wu S, Zhang Y \u0026amp; Chen Z, \u0026quot;Investigation of the dynamic modulus of asphalt mixtures containing reclaimed asphalt pavement (RAP)\u0026quot;, \u003cem\u003eConstruction and Building Materials\u003c/em\u003e, v.31, pp.50-56, 2012, https://doi.org/10.1016/j.conbuildmat.2011.12.075.\u003c/li\u003e\n\u003cli\u003eZhao Z, Xiao F, Amirkhanian S, \u0026ldquo;Recent applications of waste solid materials in pavement engineering\u0026rdquo;, \u003cem\u003eWaste Management,\u003c/em\u003e v.108, pp.78\u0026ndash;105, 2020.\u003c/li\u003e\n\u003cli\u003eZhang And Liu, \u0026quot;Investigation of XRD Analysis on Reclaimed Asphalt Pavement (RAP) to Understand Material Properties and Aging Effects\u0026quot;, \u003cem\u003eConstruction and Building Materials\u003c/em\u003e, v.227, pp.1166\u0026ndash;1176, 2019, https://doi.org/10.1016/j.conbuildmat.2019.116566.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Reclaimed asphalt pavement, Virgin aggregate, Cement, Fly ash, GGBS, base, Sub base course","lastPublishedDoi":"10.21203/rs.3.rs-6961746/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6961746/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe recycling of asphalt pavement has become a widely accepted practice in the transportation industry, driven by environmental, economic, and social benefits. Reclaimed Asphalt Pavement (RAP) consists of materials obtained from existing asphalt pavements that are no longer viable for reconstruction or resurfacing. Before RAP can be reused in construction, especially in base and subbase layers, it must undergo laboratory testing to verify its suitability. While many transportation agencies have embraced the use of RAP in unbound layers, its application is often restricted due to its relatively low strength, necessitating the use of stabilizing additives. To overcome this limitation, recent research efforts have focused on enhancing the performance of RAP by blending it with industrial byproducts. This study investigates the effectiveness of combining RAP with cement, fly ash, and ground granulated blast furnace slag (GGBS) to produce sustainable, high-performance pavement materials. Laboratory tests were carried out to assess the physical characteristics and mechanical performance of various mix combinations. A key focus of this study was to evaluate a mixture containing 50% RAP and 50% virgin aggregate (VA), stabilized with 7% cement. This specific blend demonstrated a compressive strength of 4.5 MPa, indicating its suitability for pavement applications. Among the various combinations tested, the 50:50 RAP:VA mixture with cement showed superior performance. It not only met the required strength criteria but also offered significant cost and environmental benefits by reducing the need for natural aggregates and lowering overall construction expenses. Incorporating RAP with stabilizing agents such as cement, fly ash, and GGBS significantly enhances the strength and durability of the final product, making it a viable and sustainable option for modern pavement construction. As the transportation sector increasingly emphasizes sustainability, integrating recycled materials like RAP into infrastructure projects will be critical in achieving long-term environmental goals and building resilient road systems.\u003c/p\u003e","manuscriptTitle":"Enhancing RAP-Based Pavement Layers with Industrial Byproduct Blends for Improved Performance and Sustainability","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-30 11:21:43","doi":"10.21203/rs.3.rs-6961746/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2025-10-02T17:21:37+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-07-31T03:29:23+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-25T09:50:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-15T05:47:34+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2025-07-11T03:16:01+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"66057033-7a43-442c-a5ed-ad68ed135fbf","owner":[],"postedDate":"July 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2025-10-02T21:22:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-30 11:21:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6961746","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6961746","identity":"rs-6961746","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}