Lc3 Blends for Sustainable Strength in Concrete

Lc3 Blends for Sustainable Strength in Concrete | 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 Lc3 Blends for Sustainable Strength in Concrete Suehail Aijaz Shah, Manzoor Ahmad Tantray, Arooba Rafiq Bhat, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8539713/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The construction industry is expanding rapidly, with cement serving as a critical binding material. However, the rising demand for cement has raised serious environmental concerns, including raw material depletion and significant CO 2 emissions, contributing to an increased carbon footprint. As a result, alternative binders have gained interest among researchers, with Limestone Calcined Clay Cement (LC3) emerging as a promising solution. This study presents a comparative evaluation of Ordinary Portland Cement (OPC) and a prepared mix of LC3, focusing on mechanical performance and environmental sustainability. An experimental investigation was conducted to compare the relevant properties of both Ordinary Portland Cement (OPC) and a prepared LC3 mix, aimed at evaluating their structural performance. Results indicate that LC3 achieves structural performance comparable to OPC while significantly reducing CO 2 emissions. The findings support LC3 as a viable low-carbon alternative in modern construction, offering a sustainable pathway to meet future infrastructure demands without compromising strength or performance. Compressive Strength Finesse Limestone Calcined Clay Metakaolin Ordinary Portland Cement Setting Time Sustainability Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Cement is a fundamental material in the construction industry, serving as the primary binder in concrete and mortar. Its hydraulic properties enable it to set and harden when mixed with water, forming the basis for strong and durable structural elements [ 1 ] . As of 2024, the global cement market was valued at approximately USD 403.70 billion, with an estimated consumption of around 3,866 million tonnes (Mt) [ 2 ] . The Asia-Pacific region, particularly countries like China and India, dominates global cement usage due to rapid urbanization and large-scale infrastructure projects. Cement is widely used in residential, commercial, and public infrastructure projects, playing a vital role in the construction of foundations, roads, bridges, and high-rise buildings. India, the second-largest cement producer in the world, continues to experience rising demand, driven by governmental initiatives in housing, transportation, and urban development. Its versatility, widespread availability, and reliable performance have made cement indispensable in modern construction practices, supporting the growth of the built environment across the globe. The global cement market is projected to expand steadily, with a compound annual growth rate (CAGR) of 5.40%, potentially reaching USD 683.07 billion by 2034. Despite a modest year-on-year growth forecast of 0.3% in 2025, the overall demand trend reflects the continued global reliance on cement-based construction. Cement production, though vital to modern infrastructure, presents significant environmental challenges. One of the most critical concerns is the substantial emission of carbon dioxide (CO 2 ) associated with the manufacturing process. On average, approximately 0.9 tonnes of CO 2 are emitted for every tonne of cement produced [ 3 ] . This is primarily due to the calcination of limestone (CaCO 3 ) into lime (CaO) and the combustion of fossil fuels required to heat rotary kilns. Collectively, these processes contribute to nearly 7–8% of global anthropogenic CO 2 emissions, positioning the cement industry among the largest industrial contributors to climate change. Beyond greenhouse gas emissions, cement production also leads to the extensive depletion of natural resources [ 4 ] . The extraction of raw materials such as limestone, clay, and gypsum results in land degradation, loss of biodiversity, and the generation of dust and particulate matter, which further contribute to air and water pollution. In light of these environmental impacts, there is an increasing emphasis within the research and construction sectors on developing low-carbon alternatives, enhancing energy efficiency, and encouraging the utilization of industrial byproducts all aimed at mitigating the ecological footprint of cement production without compromising its structural performance. In response to the growing environmental concerns associated with Ordinary Portland Cement (OPC) production, the construction and materials science communities have intensified efforts to develop alternative binders that offer both sustainability and performance. The integration of Supplementary Cementitious Materials (SCMs) into cement systems has emerged as a prominent strategy to mitigate the environmental impacts of Ordinary Portland Cement (OPC) [ 5 ] . Widely used SCMs, including fly ash, ground granulated blast furnace slag (GGBS), silica fume, and natural pozzolans, have been shown to improve the durability, strength, and sustainability of concrete. These materials react with calcium hydroxide during hydration to form additional calcium silicate hydrate (C-S-H) gel, enhancing the microstructure and reducing the permeability of concrete. One such promising innovation is Limestone Calcined Clay Cement (LC3) blended cement composed primarily of clinker, calcined clay, limestone, and gypsum. LC3 stands out as a low-carbon alternative to OPC, capable of reducing CO 2 emissions by up to 40% without compromising on strength or durability. The combination of calcined clay (rich in reactive alumina) and limestone leads to the formation of calcium-alumino-silicate hydrate (C-A-S-H), contributing to mechanical strength and durability [ 6 ] . Its formulation leverages calcined clay and finely ground limestone, both of which are abundantly available and require significantly less energy to process compared to clinker. The synergy between metakaolin-rich calcined clay and limestone contributes to the formation of additional calcium alumino-silicate hydrate (C-A-S-H) phases, enhancing both the early and long-term mechanical properties of concrete [ 7 ] . Beyond emissions reduction, LC3 also addresses issues of resource efficiency, enabling partial replacement of energy and carbon-intensive clinker with sustainable materials. The investigation involved the preparation of a blended mixture to formulate LC3, followed by a comparative evaluation of its properties against Ordinary Portland Cement (OPC). The key parameters assessed included fineness, water demand, initial and final setting time, and compressive strength. In addition, a micro-structural analysis was performed to examine the internal morphology and hydration products of the LC3 mix in relation to OPC. This multi-faceted approach aimed to provide a comprehensive understanding of the mechanical and physical behavior of LC3 as a potential alternative to conventional cement. Its potential for widespread adoption is particularly significant in developing regions, where access to clay and limestone is often more feasible than importing high-grade cement. As such, LC3 represents a transformative step toward sustainable infrastructure development, aligning with global goals for carbon neutrality and environmentally responsible construction practices. 2. Material & Mixture 2.1 Ordinary Portland Cement Ordinary Portland Cement (OPC) of 43 grade (Khyber Brand) was used as the primary binder for the control mix. OPC 43 grade is widely used in general construction due to its balanced strength development and compliance with IS 8112:2013 [ 8 ] . The cement was collected from a fresh batch supplied by a local manufacturer to ensure consistency and avoid any deterioration due to aging. It was stored in airtight conditions to prevent exposure to moisture prior to use in the experimental investigation. The physical and chemical properties of metakapol used are shown in Table 1 . Table 1 Physical Characteristics and properties of Cement Form Powder Colour Grey Specific gravity 3.14 Consistency 29.6% 2.2 Calcined Clay (Metakaolin) In this research program, High Reactive Metakaolin, a natural pozzolan, was employed as a partial replacement for cement. Metakaolin is a pozzolanic substance manufactured by heating kaolin to temperatures between 650 and 900°C and is non-carbon-emitting, white, and grounded. Its particle size distribution spans between 1.5 micrometers and 10 micrometers [ 9 ] . This mineral addition's dry, dense form complies with ASTM C 618 [ 10 ] class N pozzolana. Typically, it is comprised of 40–45% Al 2 O 3 and 50–55% SiO 2 and because of its large surface area 150000–180000 cm 2 /gm it is incredibly reactive [ 11 ] . Procured from Kaomin Industries LLP, Mujmahuda Vadodara. The physical and chemical properties of metakaolin used are shown in Table 2 . Table 2 Physical Characteristics and Properties of High Reactive Metakaolin Property High Reactive Metakaolin Appearance Off-white, fine powder Specific Surface Area 15,000–20,000 m²/kg Mean Particle Size (D 50 ) 1–2 µm Specific Gravity 2.5–2.6 Bulk Density 300–450 kg/m³ Fineness (retained on 45 µm sieve) 90 % Purity > 90% amorphous alumino-silicates pH 6.5–7.5 (in suspension) Loss on Ignition < 2% 2.3 Limestone Finely ground limestone (CaCO 3 ) with high purity was used as one of the key constituents. The limestone employed in this study had a minimum calcium carbonate content of 90%, ensuring optimal reactivity in the blend. It was sourced from a verified local supplier and ground to a fine particle size to enhance its surface area and improve its participation in the synergistic reaction with calcined clay. Limestone acts not only as a filler but also actively contributes to strength development through the formation of carboaluminate phases when combined with aluminates present in the calcined clay [ 12 ] . The material was dried, sieved through a 90-micron IS sieve, and stored in sealed containers to maintain its quality prior to mixing. The physical and chemical properties of limestone used are shown in Table 3 . Table 3 Physical Characteristics and Properties of Limestone Property Limestone Appearance White/grey, fine powder Specific Surface Area 3,000–5,000 m²/kg Mean Particle Size (D 50 ) 5–10 µm Specific Gravity 2.6–2.7 Bulk Density 800–1000 kg/m³ Fineness (retained on 45 µm sieve) 90% calcium carbonate (CaCO 3 ) pH (in suspension) 8.5–9.5 Loss on Ignition < 2% 2.4 Gypsum Gypsum (calcium sulfate dihydrate, CaSO 4 ·2H 2 O) was incorporated in the mix primarily to regulate the setting time of the binder system. It plays a crucial role in controlling the rapid hydration of aluminate phases, thereby preventing flash setting and ensuring adequate workability during the early stages of mixing and placement [ 13 ] . In this study, gypsum of high purity (> 95%) was procured from a certified supplier. The material was in the form of a fine powder, dried to remove any free moisture, and sieved through a 90-micron IS sieve to ensure uniform particle distribution within the mix. Its use in the blend helps to optimize the formation of ettringite during early hydration, contributing to dimensional stability and enhancing initial strength development. The physical and chemical characteristics of gypsum used in the mix design are presented in Table 4 . Table 4 Physical Characteristics and Properties of Gypsum Property Typical Value Appearance White, fine powder Purity (CaSO 4 2H₂O) > 95% Specific Gravity 2.3–2.4 Bulk Density 850–1050 kg/m³ Fineness (Retained on 90 µm sieve) < 5% Particle Size (D 50 ) 10–15 µm Moisture Content < 1.0% Loss on Ignition (LOI) 18–20% pH (in aqueous suspension) 6.5–7.5 Setting Time Impact Regulates initial & final setting 2.5 Deionized water (for mixing) Deionized water was used throughout the experimental investigation for mixing and curing purposes. It was selected to eliminate the influence of dissolved salts and impurities that may otherwise interfere with the hydration reactions of cementitious materials. The absence of ions such as calcium, magnesium, chlorides, and sulfates ensured the accuracy and reproducibility of results, particularly in microstructural and strength-related analyses. The water met the requirements specified in IS 456:2000 [ 14 ] for use in cement-based materials and was stored in clean, sealed containers to prevent contamination prior to use. 3. Proportions and Procedure for Preparing LC3 Blend 3.1 Proportions for LC3 Blend For the purpose of this investigation, a typical LC3 blend was formulated using 50% Ordinary Portland Cement, 30% metakaolin, 15% finely ground limestone, and 5% gypsum by weight. These proportions were selected based on existing existing literature and performance studies. The mix was aimd to strike a balance between reactivity and filler effects, ensuring efficient packing density, hydration kinetics, and formation of beneficial reaction products like carbo-aluminates. To simulate a practical batch size for laboratory evaluation, a 50 kg mix was prepared. The precise material quantities required for this batch are shown in Table 5 . Table 5 Material Quantities for 50 kg LC3 Blend Constituent Proportion (%) Weight (kg) Clinker 50% 25 Calcined Clay (MK) 30% 15 Limestone (CaCO 3 ) 15% 7.5 Gypsum (CaSO₄·2H 4 O) 5% 2.5 Total 100% 50 3.2 Procedure for Preparing LC3 in Lab The preparation of Limestone Calcined Clay Cement (LC3) in the laboratory involves a systematic two-step process aimed at achieving both chemical activation and homogeneity of the blend. The first stage is the production of calcined clay, which is derived from kaolinite-rich clay – metakaolin, a raw material with high pozzolanic potential. The clay is initially air-dried or oven-dried to eliminate any moisture content that could interfere with the calcination process. It is then calcined in a muffle furnace at a controlled temperature between 700°C and 850°C for a duration of 1 to 2 hours. This thermal treatment transforms kaolinite into highly reactive metakaolin, which is crucial for pozzolanic reactivity [ 15 ] . Once cooled to ambient temperature, the calcined material is finely ground to a particle size below 45 microns to maximize surface area and reactivity during blending. The second stage involves the weighing and mixing of the LC3 constituents in accordance with the predetermined mix proportions, typically comprising 50% OPC, 30% calcined clay, 15% finely ground limestone, and 5% gypsum by weight. Each component is carefully weighed using a precision balance to ensure accuracy. The dry materials are then uniformly blended using a planetary mixer to achieve a homogeneous and consistent cementitious mixture. This dry mixing phase is critical to ensuring that all materials are evenly distributed, thereby enabling reliable and repeatable results in subsequent mechanical and microstructural testing. The resulting LC3 blend is then stored in airtight containers to protect it from moisture absorption prior to further experimentation. This methodical preparation protocol ensures the production of high-quality LC3 suitable for laboratory-scale performance evaluation and comparison with conventional OPC. 4. Experimental Insights and Performance Evaluation 4.1 Fineness Test & Specific Surface Area The fineness of the cement was assessed using two complementary methods to evaluate particle size distribution and surface area, which are critical factors influencing the hydration rate and mechanical strength development. Initially, the standard IS 90-micron sieve method was employed to determine the proportion of coarser particles, reflecting the general fineness of the cement. Additionally, the specific surface area was quantified using the Blaine air permeability method, in accordance with IS: 4031 (Part 2) [ 16 ] . This technique provides a precise measurement of the cement's surface area in cm²/g, offering a more detailed insight into its reactivity. Increased fineness, indicated by higher specific surface area, enhances the rate of hydration and early strength gain by facilitating better interaction with water. These evaluations are essential for understanding and comparing the performance of Ordinary Portland Cement (OPC) and LC3 blends in terms of their physical and mechanical behavior. The results presented in Fig. 1 and Fig. 2 highlight a noticeable variation in the fineness and specific surface area between Ordinary Portland Cement (OPC) and the LC3 blend. The fineness test showed a higher residue for OPC compared to LC3, indicating that LC3 exhibits a finer particle size distribution. Conversely, the specific surface area, as determined using the Blaine air permeability method, was significantly higher for LC3 than OPC. This variation can be attributed primarily to the physical and mineralogical characteristics of the constituent materials in the LC3 blend. LC3 contains metakaolin and finely ground limestone, both of which are typically softer and finer than clinker particles used in OPC. These components, when properly ground, contribute to a higher surface area and lower residue on the 90-micron sieve. Higher Blaine fineness of LC3 suggests enhanced reactivity due to the increased surface area available for hydration. This finer particle size improves the packing density of the cementitious matrix and enhances early-age strength development [ 17 ] . In contrast, OPC, being composed predominantly of clinker and gypsum, has relatively coarser particles due to the higher grindability index of clinker compared to clay-based materials. 4.2 Specific Gravity The specific gravity of the cement samples was determined using a Le Chatelier flask, following the guidelines prescribed in IS: 4031 (Part 11) [ 18 ] . Specific gravity represents the ratio of the density of cement to the density of water, typically expressed as a dimensionless value. This property is essential for mix design calculations, influencing the volume occupied by cement in a mix and, consequently, the overall proportions and strength of the concrete. Accurate determination of specific gravity ensures precise evaluation of the material’s quality and consistency, particularly when comparing OPC and LC3 blends. The results of the specific gravity test, as shown in Fig. 3 , reveal that the LC3 mix exhibits a slightly higher specific gravity (3.14) compared to Ordinary Portland Cement (OPC), which measured at 2.95. This variation can be attributed to the denser mineralogical composition of the LC3 constituents namely, the finely ground limestone and metakaolin as calcined clay [ 19 ] . The increased specific gravity in LC3 is primarily due to the high-purity calcium carbonate in limestone and the thermally activated nature of metakaolin, both of which possess greater density than some of the less reactive components in OPC. Additionally, the synergistic interaction between limestone and metakolin contributes to the formation of denser hydration products, particularly carbo-aluminates, which further enhance the overall bulk density of the blended system [ 20 ] . 4.3 Consistency Test The standard consistency of the cement paste was assessed using the Vicat apparatus, in accordance with IS: 4031 (Part 4) [ 21 ] guidelines. This test identifies the optimal water content required to prepare a cement paste of standard workability. The normal consistency test, illustrated in Fig. 4 , indicates that the water required to achieve standard consistency is slightly higher for LC3 compared to OPC. This parameter reflects the amount of water needed to bring the cement paste to a uniform plastic state suitable for further testing, such as setting time and strength development. The marginal increase in water demand for LC3 can be attributed to the higher surface area and greater water absorption capacity of metakaolin and finely ground limestone used in the blend [ 22 ] . Calcined clay - metakaolin, being highly pozzolanic and porous due to its thermal activation, exhibits a high affinity for water. This increases the internal water demand to wet the surface adequately and ensure proper workability [ 23 ] . Additionally, the synergistic interaction between metakaolin and limestone may require slightly more water to facilitate initial dispersion and hydration reactions. 4.4 Setting Time Test Initial and final setting times were determined using the Vicat apparatus, as per IS: 4031 (Part 5) [ 24 ] . These values indicate the time intervals during which the cement transitions from a plastic to a hardened state, providing insight into workability and setting behavior. Figure 5 illustrates the comparison of initial and final setting times for Ordinary Portland Cement and Limestone Calcined Clay Cement. The results show that LC3 exhibits a slightly shorter initial setting time (87 minutes) compared to OPC (90 minutes), and a final setting time of 180 minutes versus 190 minutes for OPC. The reduction in setting times for LC3 can be attributed to the enhanced reactivity of its constituents, particularly metakaolin and finely ground limestone. Metakaolin is rich in reactive alumina, which readily reacts with calcium hydroxide released during the hydration of cement to form calcium-aluminate hydrates [ 25 ] . The presence of limestone promotes the formation of carbo-aluminate phases due to its reaction with these aluminates [ 26 ] . This synergy accelerates the early hydration kinetics and contributes to quicker stiffening of the paste. Moreover, the higher specific surface area of LC3, as demonstrated during the specific surface area evaluation, increases the contact area for hydration reactions, thereby facilitating faster initial reactions and setting. While the differences in setting times are not drastic, they are technically relevant in understanding the workability and timing for placement and finishing operations in LC3-based concretes. These results demonstrate that LC3 meets standard setting time requirements and behaves comparably to OPC. 4.5 Soundness Test The soundness of cement was tested using the Le Chatelier method as per IS: 4031 (Part 3) – 1988 [ 27 ] to evaluate its volumetric stability. This test helps detect the presence of excess free lime or magnesia, which may cause undesirable expansion after setting. The soundness test evaluates the volumetric stability of cement by measuring its tendency to undergo delayed expansion after setting. This property is primarily influenced by the presence of free lime and magnesia, which can hydrate slowly and cause expansion. In the results obtained, Ordinary Portland Cement (OPC) exhibited a soundness value of 2.5 mm, while the LC3 blend showed a lower value of 1.5 mm. Figure 6 represents the comparative soundness values of OPC and LC3, clearly highlighting the reduced expansion in LC3. This reduction can be attributed to the partial replacement of clinker with calcined clay metakaolin and limestone, which inherently possess lower levels of free lime and reactive magnesia [ 28 ] . These supplementary materials help in stabilizing the hydration process and mitigating the risk of delayed expansion, thereby enhancing volumetric stability [ 29 ] . The lower expansion observed in LC3 indicates superior dimensional stability and a reduced likelihood of unsoundness-related issues such as cracking or structural disintegration. 4.6 Compressive Strength Test Compressive strength was measured on standard 50 mm mortar cubes prepared with a cement-sand ratio of 1:3 and cured under water for 3, 7, and 28 days. The results were obtained in accordance with IS: 4031 (Part 6) [ 30 ] , providing critical data on the load-bearing capacity of the cement. Figure 7 represents the compressive strength development of Ordinary Portland Cement (OPC) and Limestone Calcined Clay Cement (LC3) at 7, 14, and 28 days. The results indicate that OPC achieved compressive strengths of 45.21 MPa, while LC3 achieved 43.16 MPa at 28 days of age. OPC demonstrated slightly higher early-age strength, primarily due to its higher clinker content, which accelerates the hydration process. In contrast, LC3, comprising approximately 50% clinker, 30% metakaolin, 15% limestone, and 5% gypsum, exhibited a more gradual strength gain, attributed to the slower pozzolanic reaction between calcined clay and lime. LC3 blend showed slightly lower early and 28-day strengths. These improvements stem from its refined microstructure and formation of additional hydration products like carbo-aluminates, which contribute to densification and long-term strength development [ 31 ] . 4.7 Microstructural Analysis Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were employed to assess the microstructural and mineralogical characteristics of the cement samples. XRD analysis provided detailed insights into the crystalline phases and hydration products, enabling identification of compounds such as portlandite, ettringite, and carbo-aluminates, which are critical for understanding the pozzolanic reactivity and phase development in both OPC and LC3 blends. Complementing this, SEM analysis was used to examine the surface morphology and internal structure at a microscale, revealing information on particle packing, porosity, and the distribution of hydration products. Together, these techniques facilitated a comprehensive evaluation of the structural integrity and performance-related features of the tested cementitious materials. 4.7.1 Microstructural Comparison Based on SEM Analysis The microstructural examination of Ordinary Portland Cement (OPC) and Limestone Calcined Clay Cement (LC3) using Scanning Electron Microscopy (SEM) reveals significant differences in morphology, porosity, and hydration product development factors that directly influence the durability and mechanical performance of the cementitious matrix. SEM analysis clearly demonstrates that LC3 possesses a refined, compact, and less porous microstructure compared to OPC. This enhanced morphology results from the combined physical filler effect and chemical interactions of the supplementary cementitious materials, making LC3 not only a sustainable option but also a technically superior material in terms of microstructural durability and integrity. In the case of OPC, the SEM images show a heterogeneous matrix characterized by large capillary pores, loosely bound hydration products, and the frequent presence of needle-like ettringite crystals. The hydration of OPC mainly leads to the formation of calcium silicate hydrate (C-S-H) gel and calcium hydroxide (CH), with the latter often visible as crystalline deposits. These features result in a relatively less compact microstructure, which is more vulnerable to permeability and environmental degradation over time [ 32 ] . The unreacted cement particles and porous zones observed suggest lower packing density and incomplete hydration, particularly at early curing stages [ 33 ] . Conversely, the SEM micrographs of LC3 reveal a much denser and more homogeneous microstructure, which is a result of the synergistic interaction between calcined clay (metakaolin) and limestone. The pozzolanic reaction between metakaolin and portlandite (CH) leads to the generation of additional C-A-S-H gel, which contributes to the refinement of pore structure [ 34 ] . Furthermore, the presence of limestone facilitates the formation of monocarboaluminate and hemicarboaluminate phases, which further densify the matrix and fill voids [ 35 ] . This densification in LC3 is evident from the reduced number and size of capillary pores and the tightly packed gel products observed under SEM. The increased surface area from calcined clay particles and the fine limestone also promotes nucleation sites for hydration, accelerating early-age strength development [ 36 ] . These microstructural improvements align with the observed higher resistance to sulfate attack, chloride ingress, and improved long-term strength performance in LC3 systems as reported in literature. 4.7.2 Crystalline Phase Development The X-Ray Diffraction (XRD) analysis of Ordinary Portland Cement (OPC) revealed the presence of distinct crystalline phases typical of hydraulic cement systems. The dominant peaks corresponded to tricalcium silicate (C 3 S) and dicalcium silicate (C 2 S), which are primarily responsible for early and long-term strength development, respectively. Additionally, significant diffraction peaks were observed for tricalcium aluminate (C 3 A) and tetracalcium aluminoferrite (C 4 AF), which contribute to the setting characteristics and influence the sulfate resistance of the cement. The intensity and sharpness of these peaks confirmed the well-crystalline nature of the clinker minerals [ 37 ] . Minor peaks indicating the presence of gypsum (CaSO 4 ·2H 2 O) were also detected, consistent with its role in controlling the setting time [ 38 ] . Overall, the XRD profile reflects the typical mineralogical composition of OPC and supports its well-established performance in conventional concrete applications. The XRD analysis of the LC3 blend revealed the presence of characteristic peaks associated with key mineralogical phases such as alite (C 3 S), belite (C 2 S), and calcium hydroxide (portlandite), indicating partial hydration of the OPC component. Additionally, distinct peaks corresponding to metakaolin-derived amorphous aluminosilicates and carboaluminate phases, such as monocarboaluminate and hemicarboaluminate, were observed [ 39 ] . These phases confirm the pozzolanic reactivity of calcined clay and the synergistic interaction with finely ground limestone. The reduced intensity of portlandite peaks, as compared to OPC, suggests higher consumption of calcium hydroxide due to pozzolanic reactions, contributing to a denser and more durable microstructure. This pattern validates the enhanced mineralogical complexity and sustainability potential of the LC3 system. The comparative analysis of the XRD patterns for OPC and LC3 reveals distinct differences in mineralogical composition and hydration behavior. The OPC sample shows prominent peaks corresponding to crystalline phases such as alite (C 3 S), belite (C 3 S), and portlandite (Ca(OH) 2 ), indicating a high clinker content and typical hydration products [ 40 ] . In contrast, the LC3 blend exhibits reduced intensity of portlandite peaks, suggesting increased consumption of calcium hydroxide due to the pozzolanic activity of calcined clay. Moreover, LC3 shows additional peaks for carboaluminate phases like monocarboaluminate and hemicarboaluminate, which are absent in OPC. These phases form due to the interaction between aluminates from metakaolin and calcium carbonate from limestone. The presence of these additional hydration products in LC3 contributes to a denser microstructure and improved durability, emphasizing the enhanced reactivity and sustainable nature of the LC3 system compared to conventional OPC. 5. Economic Analysis To assess the cost-effectiveness of LC3 (Limestone Calcined Clay Cement) compared to Ordinary Portland Cement (OPC), an economic analysis was conducted based on the cost of raw materials, blending proportions, and the overall mix cost per 50 kg batch. The market prices for each constituent material were assessed from the local market near NIT Srinagar, Hazaratbal Srinagar J&K, India, ensuring realistic and region-specific valuation for comparative evaluation. This approach helps reflect practical cost implications and supports localized decision-making for sustainable construction practices. The detailed analysis is tabulated in Table 6 . Table 6 Physical Characteristics and Properties of Gypsum Cost of 50 kg OPC Cement Material Proportion (%) Quantity (kg) Unit Cost (INR) Total Cost (INR) OPC Cement 50 9.8 490 Total Cost 490 Cost of 50 kg LC3 Mix Material Proportion (%) Quantity (kg) Unit Cost (INR) Total Cost (INR) Clinker 50 25 9.8 245 Calcined Clay (MK) 30 15 8.79 131.85 Limestone 15 7.5 3.58 26.85 Gypsum 5 2.5 7.52 18.8 Total Cost 422.5 Based on the rate analysis carried out for the raw materials, the cost of producing a 50 kg batch of LC3 mix was found to be INR 423, compared to INR 490 for an equivalent quantity of Ordinary Portland Cement (OPC). This translates to a total saving of 9.60%, demonstrating the economic advantage of LC3 over conventional OPC. The cost reduction is primarily due to the partial replacement of costly clinker with locally available and more affordable materials like calcined clay (Metakaolin) and limestone, making LC3 a cost-efficient and sustainable alternative for construction applications. 6. Conclusion SEM and XRD analyses confirmed that LC3 exhibits a more refined and denser microstructure than OPC. The presence of supplementary cementitious materials promotes the formation of additional hydration products, such as hemicarboaluminates and monocarboaluminates, which enhance the matrix integrity and contribute to long-term durability. Due to its finer particle size and higher specific surface area, LC3 facilitates more efficient water-cement interactions, resulting in improved workability and early-stage hydration. This characteristic is critical for performance optimization, particularly in high-performance and low-water binder systems. The slight variation observed in setting time and normal consistency indicates that LC3 maintains comparable setting characteristics to OPC while offering better control over workability. These characteristics are vital for adjusting field applications without compromising mechanical performance. The lower soundness value observed in LC3 reflects improved volumetric stability, owing to reduced free lime and reactive magnesia content. This enhances resistance to unsoundness-related issues such as cracking and expansion, making LC3 more stable under long-term exposure. Despite a slightly slower early strength gain, LC3 achieves compressive strength values comparable to OPC by 28 days. This validates the effectiveness of its pozzolanic and filler reactions, confirming LC3’s suitability for structural applications. The reduced clinker content in LC3 significantly lowers CO₂ emissions during production. By replacing energy-intensive clinker with calcined clay and limestone, LC3 contributes to a greener, more sustainable construction industry. A 9.60% cost saving per 50 kg mix compared to OPC was observed during the local market-based economic analysis. The use of locally available and low-cost materials not only makes LC3 cost-efficient but also reduces dependence on imported clinker, promoting regional self-sufficiency. The consistency in performance parameters, combined with cost and environmental benefits, supports LC3’s practical adoption in large-scale construction projects. Its compatibility with standard mixing and curing practices ensures a smooth transition from laboratory trials to field implementation. Scope for Future Studies While the present study affirms the viability of LC3 as a sustainable substitute for OPC, further investigation is warranted to consolidate its position in mainstream construction. Long-term durability under aggressive exposure conditions—such as sulfate attack, chloride ingress, carbonation, and freeze-thaw cycles—requires systematic evaluation to ensure applicability across diverse climatic zones and infrastructure typologies. Full-scale structural assessments of LC3 in beams, columns, and slabs are essential to validate laboratory findings and inform code development. Moreover, comprehensive studies on the rheological and mechanical behavior of LC3 in conjunction with contemporary admixtures will enable tailored mix designs for specialized applications, including high-performance and precast concrete. Life cycle assessments encompassing production, usage, and end-of-life phases are imperative to quantify environmental benefits holistically and support its inclusion in sustainability certification frameworks. Further exploration of alternative, locally sourced calcined clays and limestones can enhance regional adaptability and economic viability. Additionally, investigating LC3's integration into emerging construction technologies such as 3D printing and modular systems may extend its utility in advanced, resource-efficient building practices. Pilot-scale field applications, supported by long-term performance monitoring, will facilitate the transition from controlled experimentation to practical implementation. Finally, alignment with regulatory frameworks through the development of performance-based standards and policies will be crucial to incentivize adoption at scale. Collectively, these research directions will underpin LC3’s advancement as a technically robust and environmentally responsible binder in the future of sustainable construction. Declarations Clinical Trial Number Not Applicable. Funding Declaration This research received no external funding. Data Availability Statement: All data generated or analyzed during this study are included in this published article and its supplementary materials. All authors reviewed and approved the final version of the manuscript and agree to be accountable for the work's accuracy and integrity. Competing Interests (Conflict of Interest) Declaration The authors declare no competing interests. Ethics, Consent to Participate, and Consent to Publish declarations Not Applicable. Author Contribution Statement: Dr. Suehail Aijaz Shah: Conceptualized the research idea, designed the experimental program, supervised laboratory investigations, analyzed the results, and led the writing of the manuscript. Prof. Manzoor Ahmad Tantray: Provided technical guidance, contributed to methodological refinement, validated experimental procedures, reviewed the manuscript critically, and offered key insights for strengthening the scientific interpretation. Ms. Arooba Rafiq Bhat: Assisted in experimental work, data collection, and preparation of materials. Contributed to the literature review, data organization, and drafting of sections related to sustainable construction materials. Mr. Sajid Rafiq Bhat: Supported laboratory testing, material procurement, and sample preparation. Contributed to result tabulation, graphics preparation, and proofreading of the final manuscript. All authors reviewed and approved the final version of the manuscript and agree to be accountable for the work's accuracy and integrity. References Wilkie S, Dyer T. Mortar and concrete: precursors to modern materials. Int J Architectural Herit. 2023;18(9):1440–63. Bhardwaj A. Cement market size to exceed $ 744.34 billion by 2037 | 5.5% CAGR (2025–2037), Research Nester, 2025. Supriya N, Chaudhury R, Sharma U, Thapliyal P, Singh L. Low-CO₂ emission strategies to achieve net zero target in cement sector. J Clean Prod, 417, 2023, Article 137466. Miller SA, Habert G, Myers RJ, Harvey JT. Achieving net zero greenhouse gas emissions in the cement industry via value chain mitigation strategies. One Earth. 2021;4(10):1398–411. Thorne J, Bompa D, Funari M, Garcia-Troncoso N. Environmental impact evaluation of low-carbon concrete incorporating fly ash and limestone. Clean Mater, 12, 2024, Article 100242. Shao Z, Cao M. Hydration mechanism of limestone calcined clay cement containing calcined coal gangue. Constr Build Mater, 438, 2024, Article 136906. Luo Q, Zhang X, Yu J, Geng G. Influence of metakaolin content to the microstructure and strength in hardened LC3 paste, Cement, 2025, Article no. 100138. Bureau of Indian Standards. IS 8112:1989, Specification for 43 grade ordinary Portland cement. New Delhi: Second Revision, Bureau of Indian Standards; 1989. Ilic B, Mitrovic A, Milicic L. Thermal treatment of kaolin clay to obtain metakaolin. Hemijska Industrija. 2010;64(4):351–6. ASTM. Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete, ASTM International, West Conshohocken, PA. Thankam GL, Renganathan NT. Ideal supplementary cementing material – Metakaolin: A review. Int Rev Appl Sci Eng. 2020;11(1):58–65. Rehman MU, MacLeod AJ, Gates WP. Phase development and mechanical strength of limestone calcined clay cement utilising Australian bentonite and plasterboard waste. Constr Build Mater, 445, 2024, Article 137937. Son H, Park SM, Seo JH, Lee HK. Effect of CaSO 4 incorporation on pore structure and drying shrinkage of alkali-activated binders, Materials, 12, 10, 2019, Article 1673. Bureau of Indian, Standards. IS 456:2000, Plain and reinforced concrete – Code of practice. New Delhi: Bureau of Indian Standards; 2000. Geu MJ, Zhuge Y, Ma X, Pham TM. Optimising calcination temperature for high reactivity metakaolin: Influence on amorphous content, mineralogy and microstructure. Constr Build Mater, 489, 2025, Article 142431. Bureau of Indian, Standards. IS 4031-2:1999, Methods of physical tests for hydraulic cement, Part 2: Determination of fineness by specific surface by Blaine air permeability method. New Delhi: Bureau of Indian Standards; 1999. Oliveira DRB, Proença MP, De Souza Risson KDB, Neves A, Junior Filho JM, Possan E. Optimized cementitious matrices with activated CDW fines: A sustainable path to low carbon cement. Constr Build Mater, 483, 2025, Article 141719. Bureau of Indian, Standards. IS 4031-11:1988, Methods of physical tests for hydraulic cement, Part 11: Determination of density. New Delhi: Bureau of Indian Standards; 1988. Hu Y, Xiong L, Yan Y, Geng G. Performance of limestone calcined clay cement (LC3) incorporating low-grade marine clay, Case Studies in Construction Materials, 20, 2024, Article no. e03283. Tang J, Wei S, Li W, Ma S, Ji P, Shen X. Synergistic effect of metakaolin and limestone on the hydration properties of Portland cement. Constr Build Mater. 2019;223:177–84. Bureau of Indian, Standards. IS 4031-4:1988, Methods of physical tests for hydraulic cement, Part 4: Determination of consistency of standard cement paste. New Delhi: Bureau of Indian Standards; 1988. Takhi K, Bouhamou NE, Bouziani T, Kiboub MY. A study on fresh, mechanical and thermal properties of limestone calcined clay cement blended with cementitious materials, Studies in Engineering and Exact Sciences, 5(2), 2024, e8034. Li R, Lei L, Plank J. Impact of metakaolin content and fineness on the behavior of calcined clay blended cements admixed with HPEG PCE superplasticizer. Cem Concr Compos. 2022;133:104654. Bureau of Indian Standards. IS 4031-5:1988, Methods of physical tests for hydraulic cement, Part 5: Determination of initial and final setting times. New Delhi: Bureau of Indian Standards; 1988. Weise K, Ukrainczyk N, Koenders E. Pozzolanic reactions of metakaolin with calcium hydroxide: Review on hydrate phase formations and effect of alkali hydroxides, carbonates and sulfates. Mater Design, 231, 2023, Article 112062. Bonavetti V, Rahhal V. and, Irassar E. Studies on the carboaluminate formation in limestone filler-blended cements. Cem Concr Res. 2001;31(6):853–9. Bureau of Indian Standards, IS 4031-6:1988. Methods of physical tests for hydraulic cement, Part 6: Determination of compressive strength of hydraulic cement (other than masonry cement), First Revision. New Delhi: Bureau of Indian Standards; 1988. Sim S, Her S, Suh H, Cho S, Im S, Li P, Bae S. Influences of alumina type and sulfate content on hydration and physicochemical changes in Portland–limestone cement. Constr Build Mater, 426, 2024, Article 135989. Tsampali E, Tsardaka E, Pavlidou E, Stefanidou M. The mechanism action of crystalline admixtures on hydration, microstructure, and self-healing of cementitious materials. J Building Eng, 2025, Article 112987. Bureau of Indian Standards, IS 4031-6:1988. Methods of physical tests for hydraulic cement, Part 6: Determination of compressive strength of hydraulic cement (other than masonry cement), First Revision. New Delhi: Bureau of Indian Standards; 1988. Bogas JA, Real S, Carriço A, Abrantes J, Guedes M. Hydration and phase development of recycled cement. Cem Concr Compos, 127, 2022, Article 104405. Wu W, He X, Yang W, Alam MS, Wei B, He J. Degradation factors and microstructure degradation characteristics of B/GFRP bars in harsh environment: A review. Constr Build Mater, 366, 2023, Article 130246. Hlobil M, Kumpová I, Hlobilová A. Surface area and size distribution of cement particles in hydrating paste as indicators for the conceptualization of a cement paste representative volume element. Cem Concr Compos, 134, 2022, Article 104798. Weise K, Ukrainczyk N, Koenders E. Pozzolanic reactions of metakaolin with calcium hydroxide: Review on hydrate phase formations and effect of alkali hydroxides, carbonates and sulfates. Mater Design, 231, 2023, Article 112062. Lothenbach B, Saout GL, Gallucci E, Scrivener K. Influence of limestone on the hydration of Portland cements. Cem Concr Res. 2008;38(6):848–60. Maier M, Sposito R, Beuntner N, Thienel K. Particle characteristics of calcined clays and limestone and their impact on early hydration and sulfate demand of blended cement. Cem Concr Res, 154, 2022, Article 106736. Brown PW. Kinetics of tricalcium aluminate and tetracalcium aluminoferrite hydration in the presence of calcium sulfate. J Am Ceram Soc. 1993;76(12):2971–6. Herliati N, Sagitha A, Puspita AD, Dwi RP, Salasa A. Optimization of gypsum composition against setting time and compressive strength in clinker for PCC (Portland Composite Cement), IOP Conference Series Materials Science and Engineering, Vol. 1053, No. 1, 2021, Article no. 012116. Zunino F, Scrivener K. The reaction between metakaolin and limestone and its effect in porosity refinement and mechanical properties. Cem Concr Res, 140, 2020, Article 106307. Stutzman PE, Bullard JW, Feng P. Phase analysis of portland cement by combined quantitative X-Ray powder diffraction and scanning electron microscopy. J Res Natl Inst Stand Technol. 2016;121:1–47. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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-8539713","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":587631310,"identity":"df016cfb-ff9c-4ec0-9f36-0a3d0c65013c","order_by":0,"name":"Suehail Aijaz Shah","email":"data:image/png;base64,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","orcid":"","institution":"Kashmir College of Engineering \u0026 Technology","correspondingAuthor":true,"prefix":"","firstName":"Suehail","middleName":"Aijaz","lastName":"Shah","suffix":""},{"id":587631311,"identity":"74d32caa-c82d-4990-a993-2a9af4d2bfca","order_by":1,"name":"Manzoor Ahmad Tantray","email":"","orcid":"","institution":"National Institute of Technology Srinagar","correspondingAuthor":false,"prefix":"","firstName":"Manzoor","middleName":"Ahmad","lastName":"Tantray","suffix":""},{"id":587631312,"identity":"ebdeefde-406e-43e0-8765-ed55bb46750a","order_by":2,"name":"Arooba Rafiq Bhat","email":"","orcid":"","institution":"Government Polytechnic College Budgam","correspondingAuthor":false,"prefix":"","firstName":"Arooba","middleName":"Rafiq","lastName":"Bhat","suffix":""},{"id":587631313,"identity":"c56b4a6d-39be-455a-8b3c-70ee8d2e8b39","order_by":3,"name":"SAJID RAFIQ BHAT","email":"","orcid":"","institution":"Dr. Ambedkar Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"SAJID","middleName":"RAFIQ","lastName":"BHAT","suffix":""}],"badges":[],"createdAt":"2026-01-07 09:54:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8539713/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8539713/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102237518,"identity":"cf84d169-baed-43b5-91af-8c87464a2f15","added_by":"auto","created_at":"2026-02-09 16:32:56","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":32080,"visible":true,"origin":"","legend":"\u003cp\u003eFineness comparison between OPC and LC3 (% retained on 90-micron sieve).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/7fc670230dbbbd612861b7fa.png"},{"id":102297062,"identity":"816c629f-12b0-4726-9b96-82607b5bc991","added_by":"auto","created_at":"2026-02-10 10:25:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":61915,"visible":true,"origin":"","legend":"\u003cp\u003eSpecific surface area comparison of OPC and LC3 (cm²/g).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/acca9ff12894af6a435f51c0.png"},{"id":102297865,"identity":"61ba358d-c169-4a5c-a8e3-a54a6085292c","added_by":"auto","created_at":"2026-02-10 10:29:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":48498,"visible":true,"origin":"","legend":"\u003cp\u003eSpecific gravity comparison of OPC and LC3 samples.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/4a1cec513dd66ed13f1b3ced.png"},{"id":102297490,"identity":"f2808af1-e6e2-433b-8efd-57f142f00d25","added_by":"auto","created_at":"2026-02-10 10:27:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":56571,"visible":true,"origin":"","legend":"\u003cp\u003eNormal consistency comparison between OPC and LC3\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/a116df3c79be32b729486cff.png"},{"id":102297395,"identity":"1e60aeb4-2774-4e83-8432-43ebf5565e0b","added_by":"auto","created_at":"2026-02-10 10:27:17","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":59761,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of initial and final setting times between OPC and LC3.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/809484abec3491901cb7de33.png"},{"id":102297500,"identity":"61a5300d-d06f-4e5e-a313-3d730b6ae2ef","added_by":"auto","created_at":"2026-02-10 10:27:47","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":58969,"visible":true,"origin":"","legend":"\u003cp\u003eSoundness comparison between OPC and LC3.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/d05031f8200e46c52039af43.png"},{"id":102297431,"identity":"40939b96-e3ec-41e9-9b31-ecd6e0f99e64","added_by":"auto","created_at":"2026-02-10 10:27:25","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":72738,"visible":true,"origin":"","legend":"\u003cp\u003eCompressive strength comparison between OPC and LC3 at 7, 14, and 28 days.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/f5374e7659783b45b8ac9687.png"},{"id":102297025,"identity":"bea4b6bc-13b8-4d46-a3a3-e30fbc10ef66","added_by":"auto","created_at":"2026-02-10 10:25:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1702870,"visible":true,"origin":"","legend":"\u003cp\u003eSEM microstructure of OPC\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/21ee86755a3095e515582614.png"},{"id":102237526,"identity":"e23339c5-803a-4c87-91dd-ec15acd1a12a","added_by":"auto","created_at":"2026-02-09 16:32:56","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1636324,"visible":true,"origin":"","legend":"\u003cp\u003eSEM microstructure of LC3\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/4f01a9acbf3ea4d7fdfb2539.png"},{"id":102237522,"identity":"6e705575-a263-4b3b-a2e2-e9d082f23df7","added_by":"auto","created_at":"2026-02-09 16:32:56","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":112074,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of OPC 43 grade cement.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/c248d4323760f63c16ef1f47.png"},{"id":102237523,"identity":"3086f6aa-2eec-462a-b05b-55009798b1d7","added_by":"auto","created_at":"2026-02-09 16:32:56","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":412747,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of LC3\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/322cef9166e2a62dee1175d2.png"},{"id":103211836,"identity":"05e16f1b-ee5e-4ede-bfcc-42d8c88fa3ce","added_by":"auto","created_at":"2026-02-23 08:42:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7410845,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8539713/v1/31a24434-8e15-45a1-bcd3-93ffdcad533d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eLc3 Blends for Sustainable Strength in Concrete\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCement is a fundamental material in the construction industry, serving as the primary binder in concrete and mortar. Its hydraulic properties enable it to set and harden when mixed with water, forming the basis for strong and durable structural elements\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. As of 2024, the global cement market was valued at approximately USD 403.70\u0026nbsp;billion, with an estimated consumption of around 3,866\u0026nbsp;million tonnes (Mt)\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. The Asia-Pacific region, particularly countries like China and India, dominates global cement usage due to rapid urbanization and large-scale infrastructure projects. Cement is widely used in residential, commercial, and public infrastructure projects, playing a vital role in the construction of foundations, roads, bridges, and high-rise buildings. India, the second-largest cement producer in the world, continues to experience rising demand, driven by governmental initiatives in housing, transportation, and urban development. Its versatility, widespread availability, and reliable performance have made cement indispensable in modern construction practices, supporting the growth of the built environment across the globe. The global cement market is projected to expand steadily, with a compound annual growth rate (CAGR) of 5.40%, potentially reaching USD 683.07\u0026nbsp;billion by 2034. Despite a modest year-on-year growth forecast of 0.3% in 2025, the overall demand trend reflects the continued global reliance on cement-based construction.\u003c/p\u003e \u003cp\u003eCement production, though vital to modern infrastructure, presents significant environmental challenges. One of the most critical concerns is the substantial emission of carbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) associated with the manufacturing process. On average, approximately 0.9 tonnes of CO\u003csub\u003e2\u003c/sub\u003e are emitted for every tonne of cement produced\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. This is primarily due to the calcination of limestone (CaCO\u003csub\u003e3\u003c/sub\u003e) into lime (CaO) and the combustion of fossil fuels required to heat rotary kilns. Collectively, these processes contribute to nearly 7\u0026ndash;8% of global anthropogenic CO\u003csub\u003e2\u003c/sub\u003e emissions, positioning the cement industry among the largest industrial contributors to climate change. Beyond greenhouse gas emissions, cement production also leads to the extensive depletion of natural resources\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. The extraction of raw materials such as limestone, clay, and gypsum results in land degradation, loss of biodiversity, and the generation of dust and particulate matter, which further contribute to air and water pollution. In light of these environmental impacts, there is an increasing emphasis within the research and construction sectors on developing low-carbon alternatives, enhancing energy efficiency, and encouraging the utilization of industrial byproducts all aimed at mitigating the ecological footprint of cement production without compromising its structural performance. In response to the growing environmental concerns associated with Ordinary Portland Cement (OPC) production, the construction and materials science communities have intensified efforts to develop alternative binders that offer both sustainability and performance. The integration of Supplementary Cementitious Materials (SCMs) into cement systems has emerged as a prominent strategy to mitigate the environmental impacts of Ordinary Portland Cement (OPC)\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Widely used SCMs, including fly ash, ground granulated blast furnace slag (GGBS), silica fume, and natural pozzolans, have been shown to improve the durability, strength, and sustainability of concrete. These materials react with calcium hydroxide during hydration to form additional calcium silicate hydrate (C-S-H) gel, enhancing the microstructure and reducing the permeability of concrete.\u003c/p\u003e \u003cp\u003eOne such promising innovation is Limestone Calcined Clay Cement (LC3) blended cement composed primarily of clinker, calcined clay, limestone, and gypsum. LC3 stands out as a low-carbon alternative to OPC, capable of reducing CO\u003csub\u003e2\u003c/sub\u003e emissions by up to 40% without compromising on strength or durability. The combination of calcined clay (rich in reactive alumina) and limestone leads to the formation of calcium-alumino-silicate hydrate (C-A-S-H), contributing to mechanical strength and durability\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. Its formulation leverages calcined clay and finely ground limestone, both of which are abundantly available and require significantly less energy to process compared to clinker. The synergy between metakaolin-rich calcined clay and limestone contributes to the formation of additional calcium alumino-silicate hydrate (C-A-S-H) phases, enhancing both the early and long-term mechanical properties of concrete\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. Beyond emissions reduction, LC3 also addresses issues of resource efficiency, enabling partial replacement of energy and carbon-intensive clinker with sustainable materials.\u003c/p\u003e \u003cp\u003eThe investigation involved the preparation of a blended mixture to formulate LC3, followed by a comparative evaluation of its properties against Ordinary Portland Cement (OPC). The key parameters assessed included fineness, water demand, initial and final setting time, and compressive strength. In addition, a micro-structural analysis was performed to examine the internal morphology and hydration products of the LC3 mix in relation to OPC. This multi-faceted approach aimed to provide a comprehensive understanding of the mechanical and physical behavior of LC3 as a potential alternative to conventional cement. Its potential for widespread adoption is particularly significant in developing regions, where access to clay and limestone is often more feasible than importing high-grade cement. As such, LC3 represents a transformative step toward sustainable infrastructure development, aligning with global goals for carbon neutrality and environmentally responsible construction practices.\u003c/p\u003e"},{"header":"2. Material \u0026 Mixture","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Ordinary Portland Cement\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eOrdinary Portland Cement (OPC) of 43 grade (Khyber Brand) was used as the primary binder for the control mix. OPC 43 grade is widely used in general construction due to its balanced strength development and compliance with IS 8112:2013\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. The cement was collected from a fresh batch supplied by a local manufacturer to ensure consistency and avoid any deterioration due to aging. It was stored in airtight conditions to prevent exposure to moisture prior to use in the experimental investigation. The physical and chemical properties of metakapol used are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\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\u003ePhysical Characteristics and properties of Cement\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eForm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePowder\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eColour\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGrey\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific gravity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConsistency\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.6%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Calcined Clay (Metakaolin)\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eIn this research program, High Reactive Metakaolin, a natural pozzolan, was employed as a partial replacement for cement. Metakaolin is a pozzolanic substance manufactured by heating kaolin to temperatures between 650 and 900\u0026deg;C and is non-carbon-emitting, white, and grounded. Its particle size distribution spans between 1.5 micrometers and 10 micrometers\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. This mineral addition's dry, dense form complies with ASTM C 618\u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e class N pozzolana. Typically, it is comprised of 40\u0026ndash;45% Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and 50\u0026ndash;55% SiO\u003csub\u003e2\u003c/sub\u003e and because of its large surface area 150000\u0026ndash;180000 cm\u003csup\u003e2\u003c/sup\u003e/gm it is incredibly reactive\u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e. Procured from Kaomin Industries LLP, Mujmahuda Vadodara. The physical and chemical properties of metakaolin used are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\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\u003ePhysical Characteristics and Properties of High Reactive Metakaolin\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHigh Reactive Metakaolin\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAppearance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOff-white, fine powder\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Surface Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15,000\u0026ndash;20,000 m\u0026sup2;/kg\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean Particle Size (D\u003csub\u003e50\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u0026ndash;2 \u0026micro;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Gravity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.5\u0026ndash;2.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBulk Density\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e300\u0026ndash;450 kg/m\u0026sup3;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFineness (retained on 45 \u0026micro;m sieve)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePozzolanic Reactivity Index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;90 %\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePurity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;90% amorphous alumino-silicates\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.5\u0026ndash;7.5 (in suspension)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLoss on Ignition\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Limestone\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFinely ground limestone (CaCO\u003csub\u003e3\u003c/sub\u003e) with high purity was used as one of the key constituents. The limestone employed in this study had a minimum calcium carbonate content of 90%, ensuring optimal reactivity in the blend. It was sourced from a verified local supplier and ground to a fine particle size to enhance its surface area and improve its participation in the synergistic reaction with calcined clay. Limestone acts not only as a filler but also actively contributes to strength development through the formation of carboaluminate phases when combined with aluminates present in the calcined clay\u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. The material was dried, sieved through a 90-micron IS sieve, and stored in sealed containers to maintain its quality prior to mixing. The physical and chemical properties of limestone used are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \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\u003ePhysical Characteristics and Properties of Limestone\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLimestone\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAppearance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWhite/grey, fine powder\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Surface Area\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3,000\u0026ndash;5,000 m\u0026sup2;/kg\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean Particle Size (D\u003csub\u003e50\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u0026ndash;10 \u0026micro;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Gravity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.6\u0026ndash;2.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBulk Density\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e800\u0026ndash;1000 kg/m\u0026sup3;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFineness (retained on 45 \u0026micro;m sieve)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;5%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePozzolanic Reactivity Index\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNon-pozzolanic %\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePurity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;90% calcium carbonate (CaCO\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH (in suspension)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.5\u0026ndash;9.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLoss on Ignition\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Gypsum\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eGypsum (calcium sulfate dihydrate, CaSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO) was incorporated in the mix primarily to regulate the setting time of the binder system. It plays a crucial role in controlling the rapid hydration of aluminate phases, thereby preventing flash setting and ensuring adequate workability during the early stages of mixing and placement\u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. In this study, gypsum of high purity (\u0026gt;\u0026thinsp;95%) was procured from a certified supplier. The material was in the form of a fine powder, dried to remove any free moisture, and sieved through a 90-micron IS sieve to ensure uniform particle distribution within the mix. Its use in the blend helps to optimize the formation of ettringite during early hydration, contributing to dimensional stability and enhancing initial strength development. The physical and chemical characteristics of gypsum used in the mix design are presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\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\u003ePhysical Characteristics and Properties of Gypsum\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTypical Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAppearance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eWhite, fine powder\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePurity (CaSO\u003csub\u003e4\u003c/sub\u003e2H₂O)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;95%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific Gravity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.3\u0026ndash;2.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBulk Density\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e850\u0026ndash;1050 kg/m\u0026sup3;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFineness (Retained on 90 \u0026micro;m sieve)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;5%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParticle Size (D\u003csub\u003e50\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u0026ndash;15 \u0026micro;m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMoisture Content\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;1.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLoss on Ignition (LOI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18\u0026ndash;20%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH (in aqueous suspension)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.5\u0026ndash;7.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSetting Time Impact\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRegulates initial \u0026amp; final setting\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Deionized water (for mixing)\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eDeionized water was used throughout the experimental investigation for mixing and curing purposes. It was selected to eliminate the influence of dissolved salts and impurities that may otherwise interfere with the hydration reactions of cementitious materials. The absence of ions such as calcium, magnesium, chlorides, and sulfates ensured the accuracy and reproducibility of results, particularly in microstructural and strength-related analyses. The water met the requirements specified in IS 456:2000 \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e for use in cement-based materials and was stored in clean, sealed containers to prevent contamination prior to use.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Proportions and Procedure for Preparing LC3 Blend","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Proportions for LC3 Blend\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFor the purpose of this investigation, a typical LC3 blend was formulated using 50% Ordinary Portland Cement, 30% metakaolin, 15% finely ground limestone, and 5% gypsum by weight. These proportions were selected based on existing existing literature and performance studies. The mix was aimd to strike a balance between reactivity and filler effects, ensuring efficient packing density, hydration kinetics, and formation of beneficial reaction products like carbo-aluminates. To simulate a practical batch size for laboratory evaluation, a 50 kg mix was prepared. The precise material quantities required for this batch are shown in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\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\u003eMaterial Quantities for 50 kg LC3 Blend\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConstituent\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eProportion (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeight (kg)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalcined Clay (MK)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLimestone (CaCO\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGypsum (CaSO₄\u0026middot;2H\u003csub\u003e4\u003c/sub\u003eO)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Procedure for Preparing LC3 in Lab\u003c/h2\u003e \u003cp\u003eThe preparation of Limestone Calcined Clay Cement (LC3) in the laboratory involves a systematic two-step process aimed at achieving both chemical activation and homogeneity of the blend. The first stage is the production of calcined clay, which is derived from kaolinite-rich clay \u0026ndash; metakaolin, a raw material with high pozzolanic potential. The clay is initially air-dried or oven-dried to eliminate any moisture content that could interfere with the calcination process. It is then calcined in a muffle furnace at a controlled temperature between 700\u0026deg;C and 850\u0026deg;C for a duration of 1 to 2 hours. This thermal treatment transforms kaolinite into highly reactive metakaolin, which is crucial for pozzolanic reactivity\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Once cooled to ambient temperature, the calcined material is finely ground to a particle size below 45 microns to maximize surface area and reactivity during blending.\u003c/p\u003e \u003cp\u003eThe second stage involves the weighing and mixing of the LC3 constituents in accordance with the predetermined mix proportions, typically comprising 50% OPC, 30% calcined clay, 15% finely ground limestone, and 5% gypsum by weight. Each component is carefully weighed using a precision balance to ensure accuracy. The dry materials are then uniformly blended using a planetary mixer to achieve a homogeneous and consistent cementitious mixture. This dry mixing phase is critical to ensuring that all materials are evenly distributed, thereby enabling reliable and repeatable results in subsequent mechanical and microstructural testing. The resulting LC3 blend is then stored in airtight containers to protect it from moisture absorption prior to further experimentation. This methodical preparation protocol ensures the production of high-quality LC3 suitable for laboratory-scale performance evaluation and comparison with conventional OPC.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Experimental Insights and Performance Evaluation","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Fineness Test \u0026amp; Specific Surface Area\u003c/h2\u003e \u003cp\u003eThe fineness of the cement was assessed using two complementary methods to evaluate particle size distribution and surface area, which are critical factors influencing the hydration rate and mechanical strength development. Initially, the standard IS 90-micron sieve method was employed to determine the proportion of coarser particles, reflecting the general fineness of the cement. Additionally, the specific surface area was quantified using the Blaine air permeability method, in accordance with IS: 4031 (Part 2) \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. This technique provides a precise measurement of the cement's surface area in cm\u0026sup2;/g, offering a more detailed insight into its reactivity. Increased fineness, indicated by higher specific surface area, enhances the rate of hydration and early strength gain by facilitating better interaction with water. These evaluations are essential for understanding and comparing the performance of Ordinary Portland Cement (OPC) and LC3 blends in terms of their physical and mechanical behavior.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe results presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e highlight a noticeable variation in the fineness and specific surface area between Ordinary Portland Cement (OPC) and the LC3 blend. The fineness test showed a higher residue for OPC compared to LC3, indicating that LC3 exhibits a finer particle size distribution. Conversely, the specific surface area, as determined using the Blaine air permeability method, was significantly higher for LC3 than OPC. This variation can be attributed primarily to the physical and mineralogical characteristics of the constituent materials in the LC3 blend. LC3 contains metakaolin and finely ground limestone, both of which are typically softer and finer than clinker particles used in OPC. These components, when properly ground, contribute to a higher surface area and lower residue on the 90-micron sieve. Higher Blaine fineness of LC3 suggests enhanced reactivity due to the increased surface area available for hydration. This finer particle size improves the packing density of the cementitious matrix and enhances early-age strength development\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. In contrast, OPC, being composed predominantly of clinker and gypsum, has relatively coarser particles due to the higher grindability index of clinker compared to clay-based materials.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Specific Gravity\u003c/h2\u003e \u003cp\u003eThe specific gravity of the cement samples was determined using a Le Chatelier flask, following the guidelines prescribed in IS: 4031 (Part 11)\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Specific gravity represents the ratio of the density of cement to the density of water, typically expressed as a dimensionless value. This property is essential for mix design calculations, influencing the volume occupied by cement in a mix and, consequently, the overall proportions and strength of the concrete. Accurate determination of specific gravity ensures precise evaluation of the material\u0026rsquo;s quality and consistency, particularly when comparing OPC and LC3 blends.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe results of the specific gravity test, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, reveal that the LC3 mix exhibits a slightly higher specific gravity (3.14) compared to Ordinary Portland Cement (OPC), which measured at 2.95. This variation can be attributed to the denser mineralogical composition of the LC3 constituents namely, the finely ground limestone and metakaolin as calcined clay\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The increased specific gravity in LC3 is primarily due to the high-purity calcium carbonate in limestone and the thermally activated nature of metakaolin, both of which possess greater density than some of the less reactive components in OPC. Additionally, the synergistic interaction between limestone and metakolin contributes to the formation of denser hydration products, particularly carbo-aluminates, which further enhance the overall bulk density of the blended system\u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Consistency Test\u003c/h2\u003e \u003cp\u003eThe standard consistency of the cement paste was assessed using the Vicat apparatus, in accordance with IS: 4031 (Part 4)\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e guidelines. This test identifies the optimal water content required to prepare a cement paste of standard workability.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe normal consistency test, illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, indicates that the water required to achieve standard consistency is slightly higher for LC3 compared to OPC. This parameter reflects the amount of water needed to bring the cement paste to a uniform plastic state suitable for further testing, such as setting time and strength development. The marginal increase in water demand for LC3 can be attributed to the higher surface area and greater water absorption capacity of metakaolin and finely ground limestone used in the blend\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Calcined clay - metakaolin, being highly pozzolanic and porous due to its thermal activation, exhibits a high affinity for water. This increases the internal water demand to wet the surface adequately and ensure proper workability\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. Additionally, the synergistic interaction between metakaolin and limestone may require slightly more water to facilitate initial dispersion and hydration reactions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Setting Time Test\u003c/h2\u003e \u003cp\u003eInitial and final setting times were determined using the Vicat apparatus, as per IS: 4031 (Part 5)\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e. These values indicate the time intervals during which the cement transitions from a plastic to a hardened state, providing insight into workability and setting behavior. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e illustrates the comparison of initial and final setting times for Ordinary Portland Cement and Limestone Calcined Clay Cement. The results show that LC3 exhibits a slightly shorter initial setting time (87 minutes) compared to OPC (90 minutes), and a final setting time of 180 minutes versus 190 minutes for OPC.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe reduction in setting times for LC3 can be attributed to the enhanced reactivity of its constituents, particularly metakaolin and finely ground limestone. Metakaolin is rich in reactive alumina, which readily reacts with calcium hydroxide released during the hydration of cement to form calcium-aluminate hydrates\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. The presence of limestone promotes the formation of carbo-aluminate phases due to its reaction with these aluminates\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. This synergy accelerates the early hydration kinetics and contributes to quicker stiffening of the paste. Moreover, the higher specific surface area of LC3, as demonstrated during the specific surface area evaluation, increases the contact area for hydration reactions, thereby facilitating faster initial reactions and setting. While the differences in setting times are not drastic, they are technically relevant in understanding the workability and timing for placement and finishing operations in LC3-based concretes. These results demonstrate that LC3 meets standard setting time requirements and behaves comparably to OPC.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Soundness Test\u003c/h2\u003e \u003cp\u003eThe soundness of cement was tested using the Le Chatelier method as per IS: 4031 (Part 3) \u0026ndash; 1988\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e to evaluate its volumetric stability. This test helps detect the presence of excess free lime or magnesia, which may cause undesirable expansion after setting. The soundness test evaluates the volumetric stability of cement by measuring its tendency to undergo delayed expansion after setting. This property is primarily influenced by the presence of free lime and magnesia, which can hydrate slowly and cause expansion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the results obtained, Ordinary Portland Cement (OPC) exhibited a soundness value of 2.5 mm, while the LC3 blend showed a lower value of 1.5 mm. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e represents the comparative soundness values of OPC and LC3, clearly highlighting the reduced expansion in LC3. This reduction can be attributed to the partial replacement of clinker with calcined clay metakaolin and limestone, which inherently possess lower levels of free lime and reactive magnesia\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. These supplementary materials help in stabilizing the hydration process and mitigating the risk of delayed expansion, thereby enhancing volumetric stability\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. The lower expansion observed in LC3 indicates superior dimensional stability and a reduced likelihood of unsoundness-related issues such as cracking or structural disintegration.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e4.6 Compressive Strength Test\u003c/h2\u003e \u003cp\u003eCompressive strength was measured on standard 50 mm mortar cubes prepared with a cement-sand ratio of 1:3 and cured under water for 3, 7, and 28 days. The results were obtained in accordance with IS: 4031 (Part 6)\u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e, providing critical data on the load-bearing capacity of the cement.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e represents the compressive strength development of Ordinary Portland Cement (OPC) and Limestone Calcined Clay Cement (LC3) at 7, 14, and 28 days. The results indicate that OPC achieved compressive strengths of 45.21 MPa, while LC3 achieved 43.16 MPa at 28 days of age. OPC demonstrated slightly higher early-age strength, primarily due to its higher clinker content, which accelerates the hydration process. In contrast, LC3, comprising approximately 50% clinker, 30% metakaolin, 15% limestone, and 5% gypsum, exhibited a more gradual strength gain, attributed to the slower pozzolanic reaction between calcined clay and lime. LC3 blend showed slightly lower early and 28-day strengths. These improvements stem from its refined microstructure and formation of additional hydration products like carbo-aluminates, which contribute to densification and long-term strength development\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e4.7 Microstructural Analysis\u003c/h2\u003e \u003cp\u003eScanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were employed to assess the microstructural and mineralogical characteristics of the cement samples. XRD analysis provided detailed insights into the crystalline phases and hydration products, enabling identification of compounds such as portlandite, ettringite, and carbo-aluminates, which are critical for understanding the pozzolanic reactivity and phase development in both OPC and LC3 blends. Complementing this, SEM analysis was used to examine the surface morphology and internal structure at a microscale, revealing information on particle packing, porosity, and the distribution of hydration products. Together, these techniques facilitated a comprehensive evaluation of the structural integrity and performance-related features of the tested cementitious materials.\u003c/p\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e4.7.1 Microstructural Comparison Based on SEM Analysis\u003c/h2\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe microstructural examination of Ordinary Portland Cement (OPC) and Limestone Calcined Clay Cement (LC3) using Scanning Electron Microscopy (SEM) reveals significant differences in morphology, porosity, and hydration product development factors that directly influence the durability and mechanical performance of the cementitious matrix. SEM analysis clearly demonstrates that LC3 possesses a refined, compact, and less porous microstructure compared to OPC. This enhanced morphology results from the combined physical filler effect and chemical interactions of the supplementary cementitious materials, making LC3 not only a sustainable option but also a technically superior material in terms of microstructural durability and integrity. In the case of OPC, the SEM images show a heterogeneous matrix characterized by large capillary pores, loosely bound hydration products, and the frequent presence of needle-like ettringite crystals. The hydration of OPC mainly leads to the formation of calcium silicate hydrate (C-S-H) gel and calcium hydroxide (CH), with the latter often visible as crystalline deposits. These features result in a relatively less compact microstructure, which is more vulnerable to permeability and environmental degradation over time\u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. The unreacted cement particles and porous zones observed suggest lower packing density and incomplete hydration, particularly at early curing stages\u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. Conversely, the SEM micrographs of LC3 reveal a much denser and more homogeneous microstructure, which is a result of the synergistic interaction between calcined clay (metakaolin) and limestone. The pozzolanic reaction between metakaolin and portlandite (CH) leads to the generation of additional C-A-S-H gel, which contributes to the refinement of pore structure\u003csup\u003e[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e. Furthermore, the presence of limestone facilitates the formation of monocarboaluminate and hemicarboaluminate phases, which further densify the matrix and fill voids\u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e. This densification in LC3 is evident from the reduced number and size of capillary pores and the tightly packed gel products observed under SEM. The increased surface area from calcined clay particles and the fine limestone also promotes nucleation sites for hydration, accelerating early-age strength development\u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. These microstructural improvements align with the observed higher resistance to sulfate attack, chloride ingress, and improved long-term strength performance in LC3 systems as reported in literature.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e4.7.2 Crystalline Phase Development\u003c/h2\u003e \u003cp\u003eThe X-Ray Diffraction (XRD) analysis of Ordinary Portland Cement (OPC) revealed the presence of distinct crystalline phases typical of hydraulic cement systems. The dominant peaks corresponded to tricalcium silicate (C\u003csub\u003e3\u003c/sub\u003eS) and dicalcium silicate (C\u003csub\u003e2\u003c/sub\u003eS), which are primarily responsible for early and long-term strength development, respectively. Additionally, significant diffraction peaks were observed for tricalcium aluminate (C\u003csub\u003e3\u003c/sub\u003eA) and tetracalcium aluminoferrite (C\u003csub\u003e4\u003c/sub\u003eAF), which contribute to the setting characteristics and influence the sulfate resistance of the cement. The intensity and sharpness of these peaks confirmed the well-crystalline nature of the clinker minerals\u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. Minor peaks indicating the presence of gypsum (CaSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO) were also detected, consistent with its role in controlling the setting time\u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e. Overall, the XRD profile reflects the typical mineralogical composition of OPC and supports its well-established performance in conventional concrete applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe XRD analysis of the LC3 blend revealed the presence of characteristic peaks associated with key mineralogical phases such as alite (C\u003csub\u003e3\u003c/sub\u003eS), belite (C\u003csub\u003e2\u003c/sub\u003eS), and calcium hydroxide (portlandite), indicating partial hydration of the OPC component. Additionally, distinct peaks corresponding to metakaolin-derived amorphous aluminosilicates and carboaluminate phases, such as monocarboaluminate and hemicarboaluminate, were observed\u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e. These phases confirm the pozzolanic reactivity of calcined clay and the synergistic interaction with finely ground limestone. The reduced intensity of portlandite peaks, as compared to OPC, suggests higher consumption of calcium hydroxide due to pozzolanic reactions, contributing to a denser and more durable microstructure. This pattern validates the enhanced mineralogical complexity and sustainability potential of the LC3 system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe comparative analysis of the XRD patterns for OPC and LC3 reveals distinct differences in mineralogical composition and hydration behavior. The OPC sample shows prominent peaks corresponding to crystalline phases such as alite (C\u003csub\u003e3\u003c/sub\u003eS), belite (C\u003csub\u003e3\u003c/sub\u003eS), and portlandite (Ca(OH)\u003csub\u003e2\u003c/sub\u003e), indicating a high clinker content and typical hydration products\u003csup\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e. In contrast, the LC3 blend exhibits reduced intensity of portlandite peaks, suggesting increased consumption of calcium hydroxide due to the pozzolanic activity of calcined clay. Moreover, LC3 shows additional peaks for carboaluminate phases like monocarboaluminate and hemicarboaluminate, which are absent in OPC. These phases form due to the interaction between aluminates from metakaolin and calcium carbonate from limestone. The presence of these additional hydration products in LC3 contributes to a denser microstructure and improved durability, emphasizing the enhanced reactivity and sustainable nature of the LC3 system compared to conventional OPC.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"5. Economic Analysis","content":"\u003cp\u003eTo assess the cost-effectiveness of LC3 (Limestone Calcined Clay Cement) compared to Ordinary Portland Cement (OPC), an economic analysis was conducted based on the cost of raw materials, blending proportions, and the overall mix cost per 50 kg batch. The market prices for each constituent material were assessed from the local market near NIT Srinagar, Hazaratbal Srinagar J\u0026amp;K, India, ensuring realistic and region-specific valuation for comparative evaluation. This approach helps reflect practical cost implications and supports localized decision-making for sustainable construction practices. The detailed analysis is tabulated in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\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 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysical Characteristics and Properties of Gypsum\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=\"left\" 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\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eCost of 50 kg OPC Cement\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eProportion (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eQuantity (kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eUnit Cost (INR)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTotal Cost (INR)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOPC Cement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e490\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eTotal Cost\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e490\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCost of 50 kg LC3 Mix\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMaterial\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eProportion (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eQuantity (kg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eUnit Cost (INR)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eTotal Cost (INR)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClinker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e245\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalcined Clay (MK)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e131.85\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLimestone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26.85\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGypsum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eTotal Cost\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e422.5\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\u003eBased on the rate analysis carried out for the raw materials, the cost of producing a 50 kg batch of LC3 mix was found to be INR 423, compared to INR 490 for an equivalent quantity of Ordinary Portland Cement (OPC). This translates to a total saving of 9.60%, demonstrating the economic advantage of LC3 over conventional OPC. The cost reduction is primarily due to the partial replacement of costly clinker with locally available and more affordable materials like calcined clay (Metakaolin) and limestone, making LC3 a cost-efficient and sustainable alternative for construction applications.\u003c/p\u003e"},{"header":"6. Conclusion","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eSEM and XRD analyses confirmed that LC3 exhibits a more refined and denser microstructure than OPC. The presence of supplementary cementitious materials promotes the formation of additional hydration products, such as hemicarboaluminates and monocarboaluminates, which enhance the matrix integrity and contribute to long-term durability.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDue to its finer particle size and higher specific surface area, LC3 facilitates more efficient water-cement interactions, resulting in improved workability and early-stage hydration. This characteristic is critical for performance optimization, particularly in high-performance and low-water binder systems.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe slight variation observed in setting time and normal consistency indicates that LC3 maintains comparable setting characteristics to OPC while offering better control over workability. These characteristics are vital for adjusting field applications without compromising mechanical performance.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe lower soundness value observed in LC3 reflects improved volumetric stability, owing to reduced free lime and reactive magnesia content. This enhances resistance to unsoundness-related issues such as cracking and expansion, making LC3 more stable under long-term exposure.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDespite a slightly slower early strength gain, LC3 achieves compressive strength values comparable to OPC by 28 days. This validates the effectiveness of its pozzolanic and filler reactions, confirming LC3\u0026rsquo;s suitability for structural applications.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe reduced clinker content in LC3 significantly lowers CO₂ emissions during production. By replacing energy-intensive clinker with calcined clay and limestone, LC3 contributes to a greener, more sustainable construction industry.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eA 9.60% cost saving per 50 kg mix compared to OPC was observed during the local market-based economic analysis. The use of locally available and low-cost materials not only makes LC3 cost-efficient but also reduces dependence on imported clinker, promoting regional self-sufficiency.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe consistency in performance parameters, combined with cost and environmental benefits, supports LC3\u0026rsquo;s practical adoption in large-scale construction projects. Its compatibility with standard mixing and curing practices ensures a smooth transition from laboratory trials to field implementation.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e "},{"header":"Scope for Future Studies","content":"\u003cp\u003eWhile the present study affirms the viability of LC3 as a sustainable substitute for OPC, further investigation is warranted to consolidate its position in mainstream construction. Long-term durability under aggressive exposure conditions\u0026mdash;such as sulfate attack, chloride ingress, carbonation, and freeze-thaw cycles\u0026mdash;requires systematic evaluation to ensure applicability across diverse climatic zones and infrastructure typologies. Full-scale structural assessments of LC3 in beams, columns, and slabs are essential to validate laboratory findings and inform code development. Moreover, comprehensive studies on the rheological and mechanical behavior of LC3 in conjunction with contemporary admixtures will enable tailored mix designs for specialized applications, including high-performance and precast concrete. Life cycle assessments encompassing production, usage, and end-of-life phases are imperative to quantify environmental benefits holistically and support its inclusion in sustainability certification frameworks.\u003c/p\u003e\n\u003cp\u003eFurther exploration of alternative, locally sourced calcined clays and limestones can enhance regional adaptability and economic viability. Additionally, investigating LC3\u0026apos;s integration into emerging construction technologies such as 3D printing and modular systems may extend its utility in advanced, resource-efficient building practices. Pilot-scale field applications, supported by long-term performance monitoring, will facilitate the transition from controlled experimentation to practical implementation. Finally, alignment with regulatory frameworks through the development of performance-based standards and policies will be crucial to incentivize adoption at scale. Collectively, these research directions will underpin LC3\u0026rsquo;s advancement as a technically robust and environmentally responsible binder in the future of sustainable construction.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cu\u003eClinical Trial Number\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eFunding Declaration\u003c/u\u003e\u003cu\u003e\u0026nbsp;\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eData Availability Statement:\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article and its supplementary materials.\u003c/p\u003e\n\u003cp\u003eAll authors reviewed and approved the final version of the manuscript and agree to be accountable for the work\u0026apos;s accuracy and integrity.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eCompeting Interests (Conflict of Interest) Declaration\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eEthics, Consent to Participate, and Consent to Publish declarations\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eAuthor Contribution Statement:\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eDr. Suehail Aijaz Shah: Conceptualized the research idea, designed the experimental program, supervised laboratory investigations, analyzed the results, and led the writing of the manuscript.\u003c/p\u003e\n\u003cp\u003eProf. Manzoor Ahmad Tantray: Provided technical guidance, contributed to methodological refinement, validated experimental procedures, reviewed the manuscript critically, and offered key insights for strengthening the scientific interpretation.\u003c/p\u003e\n\u003cp\u003eMs. Arooba Rafiq Bhat: Assisted in experimental work, data collection, and preparation of materials. Contributed to the literature review, data organization, and drafting of sections related to sustainable construction materials.\u003c/p\u003e\n\u003cp\u003eMr. Sajid Rafiq Bhat: Supported laboratory testing, material procurement, and sample preparation. Contributed to result tabulation, graphics preparation, and proofreading of the final manuscript.\u003c/p\u003e\n\u003cp\u003eAll authors reviewed and approved the final version of the manuscript and agree to be accountable for the work\u0026apos;s accuracy and integrity.\u003c/p\u003e"},{"header":"References ","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWilkie S, Dyer T. Mortar and concrete: precursors to modern materials. Int J Architectural Herit. 2023;18(9):1440\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhardwaj A. 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J Res Natl Inst Stand Technol. 2016;121:1\u0026ndash;47.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Compressive Strength, Finesse, Limestone, Calcined Clay, Metakaolin, Ordinary Portland Cement, Setting Time, Sustainability","lastPublishedDoi":"10.21203/rs.3.rs-8539713/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8539713/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe construction industry is expanding rapidly, with cement serving as a critical binding material. However, the rising demand for cement has raised serious environmental concerns, including raw material depletion and significant CO\u003csub\u003e2\u003c/sub\u003e emissions, contributing to an increased carbon footprint. As a result, alternative binders have gained interest among researchers, with Limestone Calcined Clay Cement (LC3) emerging as a promising solution. This study presents a comparative evaluation of Ordinary Portland Cement (OPC) and a prepared mix of LC3, focusing on mechanical performance and environmental sustainability. An experimental investigation was conducted to compare the relevant properties of both Ordinary Portland Cement (OPC) and a prepared LC3 mix, aimed at evaluating their structural performance. Results indicate that LC3 achieves structural performance comparable to OPC while significantly reducing CO\u003csub\u003e2\u003c/sub\u003e emissions. The findings support LC3 as a viable low-carbon alternative in modern construction, offering a sustainable pathway to meet future infrastructure demands without compromising strength or performance.\u003c/p\u003e","manuscriptTitle":"Lc3 Blends for Sustainable Strength in Concrete","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-09 16:32:51","doi":"10.21203/rs.3.rs-8539713/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"54f8b56d-f5a0-4d46-a14a-ab95d17d999d","owner":[],"postedDate":"February 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-23T08:41:41+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-09 16:32:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8539713","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8539713","identity":"rs-8539713","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}