Valorization of Industrial Byproducts in Concrete: Synergistic Effects of Sewage Sludge Ash and Silica Fume with Recycled Plastic Fine Aggregates

Valorization of Industrial Byproducts in Concrete: Synergistic Effects of Sewage Sludge Ash and Silica Fume with Recycled Plastic Fine Aggregates | 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 Valorization of Industrial Byproducts in Concrete: Synergistic Effects of Sewage Sludge Ash and Silica Fume with Recycled Plastic Fine Aggregates Babatunde Olufunso Oluwole, Ömer Damdelen, Stephen Babajide Olabimtan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7207003/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract Plastics are inexpensive, lightweight, adaptable, and easily available. The manufacture of plastic has increased dramatically over the past 50 years, and its use has become an essential part of our daily life. Consequently, the production of plastic-related waste is rising, which threatens the ecosystem. Sewage sludge ash (SSA) is an inevitable waste product of wastewater treatment, and it poses a serious danger of contamination due to its high concentration of heavy metals. Various strategies are put forth globally to dispose of SSA in a sustainable and safe manner. One such method is using SSA, together with other industrial by products, to substitute cement in the creation of cementitious composites. This study explores the use of recycled plastic, sewage sludge ash, and silica fume as cement and fine aggregate substitutes. Using these materials, the study assesses the mechanical properties, workability, durability and environmental assessment of concrete, highlighting their sustainability and potential to reduce waste in the construction sector. A total of eight mixes were prepared, incorporating varying proportions of sewage sludge ash (SSA) and silica fume (SF) as partial replacements for cement, along with recycled plastic as a substitute for fine aggregate in concrete. The control mix demonstrated the best slump value among all mixes. However, mix 3 (containing 10% SF and 5% SSA) achieved the highest compressive and splitting tensile strength with an 18% and 6% increase in strength compared to the control mix after 28 days curing period. Additionally, mix 3 showed superior performance in water absorption and acid resistance tests. The environmental effect, embodied energy, and CO 2 emissions are reduced when SF, SSA, and RP are added to the concrete as an aggregate and binder. Durability Industrial by-product Mechanical Property Supplementary Cementitious Material Sustainability Sustainable concrete Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 1. Introduction The manufacturing of cement is the second-biggest industrial producer of carbon dioxide (CO 2 ) after the iron and steel sector, accounting for 7% of worldwide CO 2 emissions, based on the International Energy Agency (IEA). According to Benhelal et al., (2013), cement factories are responsible for around 5–7% of worldwide CO 2 releases; one ton of cement produces 900 kg of CO 2 emissions into the atmosphere. Significant CO 2 emissions are produced by the energy-intensive and extremely heated procedure needed to manufacture cement, and the industry's environmental effect is increased by the widespread use of concrete in building (Zeidabadi et al., 2018 ). Consequently, enhancing energy efficiency, minimizing environmental impact, and valorizing waste materials constitute fundamental challenges facing the industry (Uliasz-Bocheńczyk., 2012). There is a lot of research being done to provide environmentally friendly cement alternatives that don't affect the strength and functionality of the concrete. Accordingly, mitigating this challenge calls for systematic approaches to cut emissions in different economic domains while implementing green practices to alleviate environmental impacts (Peters et al., 2013 ). Second only to water, concrete is the most commonly used material worldwide (Bhardwaj & Kumar., 2017). It is composed of readily available and low-cost materials such as cement, aggregate, and water, making it a fundamental resource in construction. Aggregates, which make up 65–80% of the volume of concrete, are essential for defining the material's volume stability, strength, durability, workability, and permeability (Faraj et al., 2019 ). Large amounts of coarse and fine aggregates must be utilized in the manufacturing of concrete in order to fulfill the requirement for the material worldwide (Spiesz et al., 2016 ). Reducing waste buildup can be achieved by integrating waste materials into the manufacturing of concrete. This environmentally friendly method helps address the lack of natural aggregates on building sites while also reducing the negative effects of excessive aggregate mining and landfill dumping (Saikia & De Brito., 2014). Plastic is a ubiquitous substance and one of the most significant inventions of the 20th century. A significant quantity of waste is produced as a result of manufacturing operations, municipal solid waste, and service businesses (Alaloul et al., 2020 ). Massive amounts of plastic garbage are disposed of every day using unsustainable techniques, making it a serious ecological hazard. Landfilling, ocean dumping, and incineration are examples of current disposal methods that have a variety of negative environmental effects, including pollution of the land, harm to marine habitats, and air pollution from burning hazardous pollutants. The plastic recycling sector confronts significant barriers despite growing environmental demands, including: contamination issues, technological limitations in processing, low commercial viability of recycled products, costly operations, inefficient waste management systems, lack of consumer education, and mounting single-use packaging waste (Geyer et al., 2017 ). It is necessary to establish comprehensive solutions that involve cooperation amongst several sectors, including industry, government, and the general public, in order to address these issues and promote successful plastic recycling (Burgess et al., 2021 ; Wu et al., 2021). One potential strategy is to use plastic to replace aggregate in concrete. This technique allows recovered plastics to be utilized again without losing quality over time, and more significantly, it eliminates the need for virgin building materials. The physical characteristics of plastic, such as its low weight and excellent strength-to-weight ratios, make it a suitable substitute for conventional aggregate materials. Additionally, plastic can increase the durability and resilience of concrete to some kinds of damage, such water intrusion and cracking (Mehta & Monterio., 2014). The incorporation of plastic waste as a partial replacement for conventional aggregates in concrete offers dual benefits of waste reduction and enhanced material performance (Thorneycroft et al., 2018 ). Plastic aggregates demonstrate advantageous material properties including superior strength-to-weight characteristics, reduced density, and minimal water absorption - attributes that improve freeze-thaw resistance and durability in harsh environmental conditions (Ruijun et al., 2022 ). Additionally, this substitution presents environmental advantages through lower energy requirements in production compared to natural aggregates, thereby reducing the carbon footprint of concrete manufacturing. Fine aggregates were replaced in concrete by Alagusankareswari et al., 2016 , using 0%, 10%, 20%, and 30% plastic waste aggregates. Substituting 10%, 20%, and 30% fine aggregates resulted in self-weight reductions of around 3.8%, 7.25%, and 10.96%, respectively. According to the experimental findings, mechanical strength and plastic waste substitution % were inversely correlated. As plastic waste replacement rates increased, compressive strength declined by 7.6%, 21.47%, and 26.11%, while tensile strength dropped by 1.67%, 20.98%, and 38.98%. Choi et al., ( 2005 ) evaluated the fresh and mechanical qualities of concrete made with PET trash from plastic jugs as a fine aggregate alternative. When 75% PET waste plastic was used as a natural fine aggregate substitute, a 21% decrease in compressive strength was observed. Sewage sludge is an outcome of the treatment of wastewater. The removal of sewage sludge generated during sewage processing has long been a major challenge in modern society and cities. The volume of sewage sludge has grown significantly over time due to industrialization and expanding populations, and it is predicted to continue to rise. Attention over the city's surroundings have grown as a result of the substantial volumes of sewage sludge that are building up in wastewater processing facilities and the insufficient area for dumping. Sewage sludge disposal may be divided into three main categories, however there remain a lot of "unclear segments" among these clear-cut methods. These disposal methods include using it as fertilizer on agricultural land, disposing of it in the ocean, and landfilling (Ødegaard et al., 2002 ). Nowadays, the sludge produced in wastewater treatment facilities is often disposed of by landfilling (Lin et al., 2015 ). Due to a lack of landfill places (Chen et al., 2018a) and increasing worries about the spread of diseases to crops and the buildup of heavy metals on cultivatable soils, several nations have rigid rules regarding the disposal of sewage sludge (Commission, 1986 ). Modern disposal practices have been linked to environmental problems like air, water, and pollution, according to recent studies (Jamshidi et al., 2012 ). Sewage sludge dumping in the water has a negative effect on the marine ecosystem (Chung et al., 2020). This is due the bacteria that are drawn to sewage sludge absorbs a lot of oxygen to destroy the waste, which results in a shortage of oxygen in the area that is essential for marine organisms to survive (Angel, 1988 ). Sewage processing firms are now financially burdened with getting rid of sewage sludge. 7 million metric tons of sewage sludge will be produced yearly in 2020, according to Siti Noorain (2013), with management expenses reaching US $ 0.33 billion yearly. It is not deemed environmentally or economically viable to landfill sewage sludge, dispose of it in the ocean, or use it as fertilizer for the reasons listed above and the rising understanding that it may be recycled instead of disposed of. One of the alternate methods for getting rid of sewage sludge is incineration. The main ingredients of standard cements, such as SiO 2 , CaO, and Al 2 O 3 , are found in sewage sludge following high temperature incineration (Tenza-abril et al., 2011). Incorporating SSA as an alternative to cement is a sustainable option since it exhibits pozzolanic characteristics which can react with calcium hydroxide forming secondary CSH gel which improves the mechanical and durability characteristics of concrete. This is a sustainable way to lessen the environmental effects and carbon emissions linked to conventional cement manufacture. According to an experimental study done by Monzó et al., 1999, the compressive strength of cement-based mortar at 40°C after 3 to 28 days of curing is not considerably impacted by replacing 15% or 30% of the cement with SSA. According to studies, 8% SSA by mass inhibited the cement's early hydration while negatively affecting the ductility of ultra-high strength concrete (UHPC). Nevertheless, in the later phases of curing, pozzolanic reactions enhanced. The pore structure of UHPC was shown to be affected by the inclusion of SSA, leading to a reduce in large pore volume and a rise in cumulative pore volume. According to Gu et al. ( 2022 ), SSA also raised drying and autogenous shrinkage values. Furthermore, it was discovered that adding SSA to the mortar improved its compressive strength and slowed down its rate of water absorption. Another investigation by Tutur et al. (2019) examined the impact on compressive strength of replacing cement with a mixture of rice husk ash (RHA) and sewage sludge ash in different amounts (10%, 20%, 30%, 40%, and 50%). The best impact on compressive strength was found when 10% of the cement was replaced with SSA and RHA. Guo et al. ( 2023 ) discovered that while adding 10% slag and 10% fly ash enhanced overall effectiveness, adding 30% SSA decreased the mixture's flow rate and compressive strength. According to the research by Nakic et al., 2018, a 10% SSA percentage was able to attain comparable strength after three days of curing, with a little enhancement noted at seven and twenty-eight days of testing. It is recommended to use a modest percentage of SSA (usually 5–10%) to boost compressive strength because of its pozzolanic activity, which can counteract the rise in porosity caused by the porous characteristics of SSA in the concrete mix (Hassooni & Ethaib., 2020). Improved compressive strength at 28 days of curing compared to a slow strength increase at an early age for the evaluated SSA concrete mixes, according to research by Xia et al., 2023. The author attributed this behavior to the existence of PO 4 3− in the SSA, which disintegrates in the mix and prevents the hydration of C3S in cement at an early age, as well as the greater absorption of water for the SSA particles, which would be discharged at older ages in order to promote the hydration process. The construction industry has increasingly adopted silica fume as a pozzolanic additive in recent years. When incorporated at optimal percentages, it effectively improves concrete performance in its plastic and cured states boosting cohesion, mechanical strength, permeability, and overall durability. The airborne dissemination of silica fume, a byproduct of the smelting of silicon-based alloys (such as calcium silicon, ferro-chromium, and ferro-manganese), can cause occupational health issues and environmental deterioration. This pozzolanic material serves dual purposes in concrete production: it can replace a portion of cement (often to lower material costs) or act as a supplementary additive to boost key properties in fresh and cured concrete, including its renowned strength-enhancing capability (‌De la Précontrainte.,1988). Numerous investigations and research projects have taken into account the use of silica fume because of its excellent outcomes. The use of silica fumes as a partial cement substitute improved the workability, mechanical strength, and aggregate interlocking of concrete (Singh et al., 2016 ). The effect of silica fume on Concrete's fresh Properties Nematzadeh and Hasan-Nattaj ( 2017 ) investigated the slump flow of very durable concrete. Their findings showed that slump decreased as the percentage of concrete that had silica fume replacement increased. According to Wu et al., 2016 , ultra-high strength concrete containing silica fume showed a discernible improvement in compressive strength findings at early ages. The study conducted by Rostami and Behfarnia., (2017) showed that increasing silica fume dosage progressively decreases concrete's water absorption capacity. Test results indicated that mixes containing 5%, 10%, and 15% silica fume exhibited 5.97%, 9.70%, and 13.06% lower water absorption than conventional concrete. Studies show that incorporating 5–15% silica fume as a cement replacement yields the highest compressive strength at 28 days. The improvement stems from silica fume's pozzolanic activity - it reacts with calcium hydroxide from cement hydration to generate more C-S-H gel, which strengthens the concrete matrix (Mohan & Hayat., 2021). Critical gaps still exist despite advancements in waste-valorized concrete: (1) combined SSA-SF-RP systems have not been investigated; (2) there is a lack of durability data for concrete, especially with regard to sulfate resistance; and (3) there is no framework in place to balance the environmental benefits and mechanical performance of these cement systems. This research addresses these gaps. Sustainable building has become an essential component of civilization due to the advancement of technology. Concrete development is therefore required due to the growing need for stronger, more resilient, and long-lasting constructions. In order to improve the sustainability of concrete, this study intends to experimentally examine the effects of partially substituting cement and sand with different amounts of silica fume, sewage sludge ash, and recycled plastic on the mechanical, physical, and durability properties of concrete. 2. Materials and Experimental Methods 2.1 Raw Materials 2.1.1 Cement, Mixing Water and Admixtures The study employed concrete mixtures prepared using CEM II type cement. The ASTM C150/C150M-21 requirements can be applied with this specific type of cement. To achieve a minimum compressive strength of 42.5 megapascals (MPa) over a 28-day curing period, the concrete was formulated using 42.5-grade cement in compliance with ASTM rules. As the mixing water for the research, regular tap water with a pH between 6.5 and 7 was utilized. The criteria of ASTM C1602/C1602M-18 were tightly followed to guarantee that all concrete mixes and the subsequent curing method were free of acids, greases, and organic impurities. A high-range water reducer called a superplasticizer was added to the mixing water in order to account for the low water-to-binder ratio. The goal of this modification was to increase the compaction process and workability. In particular, the study used a glenium-based superplasticizer. 2.1.2 Fine aggregate Particles that pass through a 4.75 mm sieve are referred to as fine aggregate. The fine aggregate selected was crushed limestone, which complies with ASTM C33/C33M-18 requirements. The sand was produced in accordance with ASTM C128-17a requirements, guaranteeing that it maintained a saturated surface dry state in order to limit water absorption during mixing. Figure 2 shows the particle size distribution of the natural aggregate utilized, and Table 1 provides more details regarding the properties of the sand. Table 1 Sand properties PROPERTIES PARAMETERS ASTM Water Absorption (%) 1.32 C128-15 Specific Gravity 2.630 C128-15 Fineness Modulus 2.79 C33/C33M-18 Moisture Content (%) 0.1 C566-19 Loss Bulk Density (kg/m 3 ) 1576 C29/C29M-17a Compact Bulk Density (Kg/m 3) 1728 C29/C29M-17a 2.1.3 Coarse aggregate The size variation of the coarse particles employed can have a major impact on the qualities of concrete, such as its strength and workability. The particle size distribution of coarse aggregates in concrete mixes may be precisely determined and controlled with the use of standards like ASTM C136M-14 and C33M-16. These guidelines guarantee that the aggregates fulfill certain requirements, improving the uniformity and performance of the final concrete. 2.1.4 Silica fume The smelting of silicon and ferrosilicon produces silica fume (SF), also known as microsilica, condensed silica fume, volatilized silica, and silica dust. It is composed of extremely thin vitreous particles and has a surface area of 13,000 to 30,000 m²/kg. It is available in white or gray colors. The high proportion of silica and its high fineness make silica fume an extremely effective pozzolanic mixture. Figures 3 & 4 illustrates the physical appearance and SEM of silica fume utilized in the study. The chemical composition of silica fume is depicted in Table 2 . Table 2 Chemical composition of silica fume Chemical Compound Silica fume CaO 0.49 SiO 2 92.26 Al 2 O3 0.89 Fe2O3 1.97 SO 3 0.33 K 2 O 1.31 Na 2 o 0.42 Tio 2 0.01 2.1.5 Recycled plastic A mixture of post-consumer polyvinyl chloride (PVC), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE) plastics was used to partially substitute fine aggregate in the manufacturing of concrete. The plastics were crushed into tiny pellets that ranged in size from 300 µm to a maximum average size of 3.0 mm. A nearby recycling plant in the Lefkosa area of the Turkish Republic of North Cyprus (TRNC) provided the plastic pellets shown in Fig. 5 . 2.1.6 Sewage Sludge Ash Sludge was taken from the waste water treatment plants disposal facility in Haspolat Nicosia. North Cyprus. Pyrolysis was used to treat sewage sludge ash in a furnace for two hours at 850°C. The ash from sewage sludge was then left to cool gradually before being ground with the Los Angeles machine to particles that passed through 75 µm sieves. Its specific gravity and water absorption were 2.72 and 0.86, respectively. Table 3 Chemical composition of sewage sludge ash Chemical Compound SEWAGE SLUDGE ASH CaO 10.15 SiO 2 24.85 Al 2 O3 9.7 Fe2O3 8.13 SO3 3.52 MGO 2.87 LOI 2.88 p 2 0 5 24.1 2.2 Experimental Methodology In addition to a reference mix, eight distinct concrete mixes were made, each with a different amount of silica fume and sewage sludge ash added to partially replace cement and fine aggregate replaced with recycled plastic. In order to maintain a constant water-to-binder ratio of 0.50, superplasticizer was applied evenly. This study looks at the feasibility of employing these waste products in the production of concrete, as well as promoting sustainable construction practices and reducing the environmental impact of conventional materials. 2.2.1 Mix Design Identifying the amounts and ratios of key ingredients in concrete mixtures to provide the required workability, characteristic strength, and peculiar material qualities is the fundamental definition of design mix. In this work, concrete made from silica fume, Sewage sludge ash, and recycled plastic was constructed utilizing eight different combinations and the experimental approach. To determine the characteristics and ratios of the mixtures, which include the sand-to-binder (cement, silica fume, Sewage sludge ash) and water-to-binder ratios, the first step was to create experimental mixes. The design of the concrete mix encompassing 5% SSA, 10% SF and 30% RP is based on the combination of the efficiency of the material, sustainability objectives and practical constraints. Prior to earlier researches increasing the doses of SSA culminates into decreased early strength, and silica fume over 10% increases cost and 30% Rp was adopted as a threshold which serves as an alternative to sand without significantly compromising the mechanical characteristics. The modified SP doses and the % mix design are displayed in Tables 4 and 5 . Table 4 Description of the Concrete mixes MIX ID DESCRIPTION CM Control Mix M1 10% Silica fume, 0% SSA, 0% Recycled plastic M2 0% Silica fume, 5% SSA, 0% Recycled plastic M3 10% Silica fume, 5% SSA, 0% Recycled plastic M4 0% Silica fume, 0% SSA, 30% Recycled plastic M5 10% Silica fume, 0% SSA, 30% Recycled plastic M6 0% Silica fume, 5% SSA, 30% Recycled plastic M7 10% Silica fume, 5% SSA, 30% Recycled plastic Table 5 Mix design of the Concrete mixes LABEL MIXES W/C W C SF SSA FA RP CA kg/m3 SP kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 kg/m3 10mm 20mm kg/m3 CM 0% SF; 0% SSA; 0% RP 0.5 210 420 0 0 891 0 363 726 2.1 MIX 1 10%SF; 0% SSA; 0% RP 0.5 210 378 42 0 891 0 363 726 2.1 MIX 2 0% SF; 5% SSA; 0% RP 0.5 210 399 0 21 891 0 363 726 2.1 MIX 3 10% SF; 5% SSA; 0% RP 0.5 210 357 42 21 891 0 363 726 2.1 MIX 4 0% SF; 0% SSA; 30% RP 0.5 210 420 0 0 623.7 267.3 363 726 2.1 MIX 5 10% SF; 0% SSA; 30% RP 0.5 210 378 42 0 623.7 267.3 363 726 2.1 MIX 6 0% SF; 5% SSA; 30% RP 0.5 210 399 0 21 623.7 267.3 363 726 2.1 MIX 7 10% SF; 5% SSA; 30% RP 0.5 210 357 42 21 623.7 267.3 363 726 2.1 NB: w/c: water to cement ratio, W: Water, C: Cement, SF: Silica fume, SSA: Sewage Sludge Ash, F.A: Fine aggregate, RP: Recycled plastic, CA: Coarse aggregate, SP: Superplasticizer 2.2.2 Casting procedure All of the concrete blends were made according to ASTM C305-20 guidelines. The concrete mixer was used to generate each test sample. For one minute, the coarse aggregate, 50% water, and 50% cement are well mixed. Then, the remaining 50% cement, 25% water, fine aggregate, and superplasticizer are added, and the mixture is combined for three minutes. The remaining 25% water was added last, and the mixture was stirred for three more minutes. The specimens were put into cube molds (100 mm x 100 mm x 100 mm) after the mixing procedure was complete. The specimens were subjected to a number of tests to ascertain their characteristics in both fresh and hardened stages, such as the acid attack test, compressive strength, splitting tensile strength, water absorption, and dry density. Table 5 provides an overview of the tests conducted for this investigation. Table 6 Summary of experiments conducted for this study. Test Code/ standards Specimen Compressive strength ASTM C349-18 100x100x100 mm Splitting Tensile Strength ASTM C496-96 100x100x100 mm Water Absorption ASTM C1585-20 100x100x100 mm Acid Attack Test ASTM C267 100x100x100 mm 3 Result and Discussion 3.1 Workability The slump test evaluates concrete's workability, which is its capacity to flow uniformly while maintaining cohesion. Numerous factors, such as the type, quantity, and characteristics of the ingredients in the combination, affect the consistency and handling process of concrete. The properties of novel concrete may be examined by substituting some of the traditional concrete elements with silica fume, sewage sludge ash, and recycled plastic. Assessing the effects of these replacements on the consistency and workability of the mixture is made easier by the slump test results. Figure 9 shows the outcomes of the slump test, which evaluates how workable and consistent fresh concrete is. The slump measurements across the different mixes fell within the range of 33 mm to 58 mm, with the control mix recording the highest value. When compared to the control mix, mixes 1 through 7 exhibited lower slump values, decreasing by 27%, 21%, 31%, 17%, 34%, 38%, and 43%, respectively with mix 7 showing the least slump. The reason for this slump decreases is due to the incorporation of the additives utilized. Silica fume requires more water for efficient lubrication due to its smaller particles and larger surface area than OPC making the concrete mixture less workable and more rigid as a result. Nedunuri et al., ( 2020 ), Mohan & Mini., 2018, also reported reduced workability as a result of silica fume's higher water consumption because of its large surface area and ultrafine particles, which is consistent with our findings. SSA's high surface area and irregular particle shape, which both encourage more water absorption at the particle interface, are also part of reasons why introducing it to cementitious systems decreases workability. The porous structure enhances water absorption capacity, while the irregular particle geometry promotes particle rearrangement within the mortar matrix, creating numerous void spaces (Lin et al., 2008). Additionally, SSA contains a greater level of P 2 O 5 , which results in a very hygroscopic matrix (Lawrence., 1998). The research outcomes of Gu et al., ( 2021 , 2022 ) aligned with these observations. The addition of recycled plastic to concrete also contributes to reduced workability and the effect occurs through two mechanisms: First, flow is impeded and internal friction is produced by the plastic particles' uneven shapes and sharp edges. Secondly, because plastics are water-repellent, air bubbles develop at the surface of the particles, creating gaps at the plastic-cement interface. Increasing the amount of RP added to the combination intensifies both effects (Záleská et al., 2018 ). Tota-Maharaj et al., 2022, reached analogous finding in their work. 3.2 Compressive strength Over the course of the 7, 14 and 28day curing periods, the different mixes showed differing strength improvements as illustrated in Fig. 10 , which was indicative of the combination’s gradual hydration and pozzolanic reactions. The cementitious ingredients continued to react as the curing period rose, resulting in the development of more calcium silicate hydrate (C-S-H) gel and greater compressive strength. Initial hydration was the main cause of the early strength at 7 days, although continuing hydration and subsequent pozzolanic reactions, especially in mixes with additional cementitious elements like silica fume and sewage sludge ash, had an impact on the later strength growth (14 and 28 days). This pattern demonstrates how extended curing greatly enhances the set material's microstructure and durability. At 7 days of curing, the control mix achieved the highest compressive strength among all mixes. Although Mix 3 (10%SF & 5%SSA) demonstrated superior strength compared to other modified mixes, it still exhibited lower early-age strength than the control. This can be attributed to the delayed pozzolanic reaction of silica fume and sewage sludge ash (SSA), which results in slower strength development at early stages. Similar findings were reported by Al Shanti et al., 2021 and Khawal and Sangwai., 2019, who observed that SSA blended concrete mixes experienced slower initial strength gain due to the reduced cement content, which hindered early hydration reactions. Since pozzolanic materials progressively react with calcium hydroxide to generate more cementitious compounds over time, the delayed strength growth is typical of these materials. Although the SSA and SF mixes may have a somewhat lower initial strength increase, strength rate gain improves during the 14 &28 day curing period (Gu et al., 2022 ). In comparison to the control mix, mix 2, which included 5% SSA, likewise shown decreased early-age strength. The high-water absorption of SSA particles, which subsequently liberated moisture to promote hydration, was associated with this activity. Furthermore, the early hydration of C₃S in the cement was impeded by the existence of PO₄³⁻ in the SSA dispersed within the mixture (Rutkowska et al., 2023 ). Mix 3 (10% SF & 5% SSA) demonstrated the highest compressive strength after 28 days of curing, showing a 18% strength improvement over the control mix. The addition of silica fume (SF) enhanced the compressive strength due to its fine particle size and strong pozzolanic reactivity. The calcium hydroxide released during cement hydration reacted with the reactive silica, forming additional CSH gel that densified the cement matrix, thereby increasing the concrete's strength. Shi et al., 2015 , research yielded comparable conclusions. In comparison to the control mix, mix 1 (10% SF) and Mix 2 (5% SSA) demonstrated strength improvements of 9% and 5%, respectively, as seen in Fig. 10 . Similar conclusions were drawn by Mohammed et al., 2024, in their research. Nevertheless, mix 3 was superior compare to both mixes. This implies that SF performs better as a cement replacement when combined with SSA, leading to increased compressive strength and the production of more ecologically friendly and sustainable building materials. Mix 4 exhibited the lowest strength among all mixes, with a 49% reduction compared to the control mix. This decline in compressive strength is likely attributed to the smooth surface of the plastic waste, leading to weak bonding between the plastic and the cement paste (Ullah et al., 2022; Almeshal et al., 2020 ). Also, the recycled plastic concrete is weakened by the formation of a thin water layer around the hydrophobic plastic granules (Pezzi et al., 2006 ). Concrete strength is also greatly influenced by the plastic waste elastic modulus. The inclusion of plastic waste with a high elastic modulus, lowers the concrete's compressive strength. In contrast to plastic waste with a greater elastic modulus, like PET aggregates, plastic waste with a lower elastic modulus, like EPA aggregates, results in a more significant reduction in compressive strength (Almeshal et al., 2020 ). The particle shape of the aggregate can compromise the compressive strength of concrete, Gu and Ozbakkaloglu found that concrete mixtures with irregularly shaped plastic waste aggregate experience a greater decrease in compressive strength than concrete mixtures with consistently shaped plastic waste aggregate. Although mixes 5,6 and 7 showed lower strength than the control mix, their performance was better than mix 4 due to the pozzolanic activity of the supplementary cementitious material (silica fume and sewage sludge ash) explained earlier. Tanli et al., 2022, Ullah et al., 2022, all arrived at similar conclusion in their respective researches. 3.3 Splitting Tensile Strength To evaluate a concrete specimen's tolerance to elongation, the splitting tensile strength test is usually performed. With a 6% increase in tensile strength above the control mix which mirrored the trend seen in the compressive strength, mix 3 (10% SF & 5% SSA) had the best performance as shown in Fig. 11 . The greater tensile strength values can be attributed to the same factor as were previously discussed for compressive strength. In comparison to the reference mix, mix 4 has the lowest tensile strength. Higher porosity, the lightweight characteristic of plastic waste aggregates, and the poor binding between the cement paste and plastic waste aggregate are some of the reasons for this decrease in tensile strength when utilizing plastic waste (Ali et al., 2021 ; Ullah et al.,2021). Plastic aggregate's smooth texture causes poor adhesion or bonding to form between it and cement paste, which reduces strength (Akinyele & Ajede., 2018). Also, the reduced density, stiffness, unit weight of plastic aggregate relative to fine aggregate culminates to high stress zones promoting damage spread accounting for strength reduction (Ahirwar et al., 2016 ). The majority of plastic waste, however, is not removed and stays embedded in the concrete sample, as demonstrated by the concrete's fracture surface in Fig. 12 . Because plastics are hydrophobic, their usage in concrete reduces the adhesive strength between them and the cement paste, which results in a reduction in tensile strength (Saikia et al., 2012). Danish & Ozbakkaloglu., 2023, arrived at similar conclusion in their studies. Although they exhibited greater strength than mix 4, mixes 5, 6, and 7 also showed less strength than the control mixes. Concrete that contains silica fume and sewage sludge ash, together with 30% plastic waste replacement (mix 7), exhibits a steady increase in tensile strength. Because silica fume and sewage sludge ash are highly reactive and encourage the production of hydration products like calcium silicate hydrate (C-S-H) gel, as well as their filler action in improving densification, this rise in tensile strength may be attributed to them. 3.4 Density The densities of the various combinations and the effects of adding silica fume and sewage sludge ash as cement substitutes and plastic aggregates as fine aggregate replacement on concrete density are contrasted in the graph in Fig. 13 . Mixes 1(10% SF), mix 2 (5% SSA) and mix 3 (10%SF, 5% SSA), exhibited density values comparable to the control mix owing to the densifying filler effect of SF and SSA particles in the cement matrix. Significant decrease in density was observed in mixes (4–7), compared to the control mix with mix 4 exhibiting 20% decrease, mix 5,6 &7 showing 21%, 21.05% & 20.42% density decrease in respect to the control mix. This is due to plastic low density and smooth sharp-edged characteristics that increase air content and decrease the dry density (Akinyele et al., 2018; Saikia et al., 2014; Colangelo et al., 2016). Another reason for the decrease is that plastic has a lower specific gravity than natural fine aggregate (Sheelan et al., 2019). Because of the decreased concrete density, the structural member's deadweight is decreased. Thus, using recycled plastic in the concrete system might be viewed as beneficial. Numerous experts concur that Yong-Woo Choi (2005) (YW. Choi et al., 2005 ) and Aldahdooh MAA (2018) found that plastics have a lower density, which causes their density to drop. 3.5 Water Absorption The durability of concrete can be evaluated through water absorption tests, as lower water absorption culminates to greater durability compared to higher water absorption which compromises the durability characteristics of concrete. Figure 14 clearly depicts the results of the water absorption test for the concrete mixes. Mix 3 (10%SF & 5% SSA) exhibited the best performance with a 33% decrease in water absorption compared to the control mix. The pozzolanic reaction of silica fume which decreased the concrete samples surface porosity, is responsible for this improvement. Another benefit is attributed to the pozzolanic activity of sewage sludge ash, which facilitated in the refinement of the microstructure, creating a denser cement matrix that prevented water penetration. The incorporation of silica fume and sewage sludge ash increased the specimen’s resistance to water penetration by decreasing their permeability when used in concrete. In situations where concrete must be water resistant, this property is essential. Mix 2 (10% SF) and mix 3 (5% SSA) displayed favorable water absorption properties with a 27% and 15% decrease in water absorption compared to the control mix. The specific surface area of silica fume which occupies the voids as well as high silica content which reacts with the calcium hydroxide forming additional CSH gel which improves the microstructure are responsible for the prevention of water permeating into the specimen. The porosity of SSA blended concrete is influenced by two factors, the refinement of the pore structure attributed to its pozzolanic reaction (Chakraborty et al., 2017 ), and the synthesis of ettringite (Aft) which may increase porosity culminating into high water absorption (Gu et al., 2019 ). Hamada et al., 2023 ; Danish & Ozbakkaloglu., 2023, reached consistent conclusions in their respective researches. In comparison to the control mix, mix 4 (30% RP) showed the highest water absorption percentage with a 42% increase. This is due to the plastic and fine aggregate improper integration into the cement matrix which exacerbated the porosity of the concrete (Saikia.,2013). The evaporation of excess water surrounding hydrophobic plastic waste aggregate, the rise in porosity in concrete caused by plastic aggregate, and the weak ITZ close to plastic particles as a result of a poor bond between the binder matrix and plastic waste aggregate could be the causes of the higher absorbing capacity in comparison to the control. Concrete using plastic aggregate showed a greater absorption percentage than conventional concrete, according to Albano et al., 2009 . On top of that, the water absorption rises when the size of the plastic particles, the amount of plastic aggregate, and the w/c ratio all increase. Raju et al. ( 2021 ) showed outcomes that were comparable. 3.6 Exposure to Acid Attack The findings, which are shown in Fig. 15 , showed that various concrete mixes diminished strength after 28 days of curing in an H 2 SO 4 acid solution. All samples demonstrated reduced strength when exposed to the sulfuric solutions. Comparing mixes 1–3 to control mix, the control mix showed the least residual strength. Concrete that comes into contact with sulfate-rich environments, such as soil or water, experiences a chemical reaction known as "sulfate attack," which shortens its lifespan. Sulfate ions enter the concrete and interact with calcium hydroxide and calcium aluminate hydrates, which are byproducts of Portland cement hydration. Ettringite, a chemical result with significant expansion and internal tension, is the outcome of this. Additionally, sulphates degrade and reduce the cohesiveness of concrete by destabilizing calcium silicate hydrate (C-S-H) (Zhang et al., 2024 ). Mix 3 showed the best resistance to acid attack, like wise mixes 1 and 2. SF's strong pozzolanic response primarily influences the enhancement of paste microstructure and increases resistance to aggressive assaults such surface scaling. Weak microstructural regions and the production of additional CSH gels are decreased by this improvement. Comparing mixes 4–7, mix 4 exhibited the least resistant to sulfuric acid. There might not be a strong chemical bond between the cementitious matrix and plastic waste particles. The entire chemical makeup of the concrete may be impacted and the hydration process may be hampered if plastic waste is included in the mix (Asokan et al., 2009 ). The concrete's ability to withstand acid and sulfate assaults may be compromised by this interference. Since plastics are non-polar, they generally resist chemical reactions with acids. However, the weak bond between the plastic aggregate and cement paste increases the porosity of the concrete. This porous structure allows sulfate solutions to penetrate reacting with the products of hydration in the cement matrix. As a result, expansive compounds like gypsum and ettringite form creating internal pressure. Since concrete lack sufficient space to accommodate these expanding products crack develop, further compromising its durability. Other precautions can be taken to lessen the impact of sulfate and acid assaults while employing plastic waste aggregates like utilizing SCM. For instance, mix 7 exhibited more resistance to acid attack compared to mix 4. Figure 16 provides a visual representation of the examination of the materials subjected to sulfuric acid, clearly showing the deterioration of the samples and the damaging impact of the sulfuric acid assault on their surface. In all mixes, white areas were seen on the concrete's surface after 28 days. Gypsum and ettringite may have formed as white patches on the surface as a result of the sulphate solution's reaction with hydration products. The concrete sample' corners and edges showed signs of degradation. These examples unequivocally demonstrate the harm caused by the materials engagement with the corrosive properties of sulfuric acid resistance. 4. Sustainability Assessment 4.1 Embodied Carbon This section covers the eCO2 emission evaluations calculations, and the performance of Eco strength efficiency evaluations of the material used, as to ascertain the sustainability of the SF, SSA and RP used as cement and fine-aggregate alternative. This focused on comparing the viability of achieving sustainable delivery of mixes containing different percentages of SF, SSA and RP with the control group, consisting of traditional concrete mixes. Due to the loss of natural resources caused by urbanization and industrialization, which intensifies global warming, researchers from all over the world are taking sustainable development into consideration. Since the concrete industry uses a lot of energy and natural resources, its greenhouse gas emissions have expanded dramatically. The mix proportion's embodied carbon is calculated with the use of existing research. Embodied carbon factors for all of the materials used to prepare concrete were extracted from the literature, and the embodied carbon of each percentage was calculated using those embedded carbon factors. Table 7 displays each material's EC factors. Table 7 Material's EC factors. Materıals Embodied carbon factors (Kg.CO2/Kg) Ref. Cement 0.82 Collins, (2010) Silica Fume 0.024 Thilakarathna et al., (2020) Sewage Sludge Ash 0.0513 Galabada et al., ( 2022 ) Recycled Plastics 0.0051 Hammond&Jones, (2008) fine aggregate 0.0139 Turner and Collins, (2013) coarse aggregate 0.0043 Alnahhal et al., ( 2018 ) Water 0 Jones et al., (2011) Superplasticizer 0.72 Kumar et al., (2021) The embodied carbon of the concrete mixes used in the study is shown in Fig. 17 . The lowest amount of embodied carbon, around 311.05 kg CO 2 /kg, was found in Mix 7. The fact that 30% RP has low embodied carbon in comparison to fine aggregate and 5% SSA 10%SF has very low embodied carbon in comparison to cement makes this clear. There was a decrease in CO 2 emissions once SCMs were added, and the substitution of plastic for fine aggregate also contributed to the decreased embodied carbon. Comparing mix 4 (30% RP) to the control mix, the embodied carbon was lower. This happened because RP was only used to replace the fine aggregates in the mix, not the cement component, which was not replaced with any other material. By reducing the quantity of plastic trash produced, using it in construction offers the benefit of reducing material costs while also taking sustainability into consideration. The rest mixes all showed reduced embodied carbon with control mix exhibiting the maximum embodied carbon of about 362.97 Kg.CO 2 /Kg. Zada et al., 2025, Kumar et al., 2022 demonstrated sımılar conclusions ın theır research. 4.2 Eco-strength Efficiency Despite being the most prevalent building materials in the world, the manufacture of concrete massively enhances emission of carbon and resources depletion. The optimization of both the environmental sustainability and the mechanical properties is termed eco strength efficiency in concrete. Eco-strength efficiency promotes sustainable construction, which attempts to lessen environmental effects, minimize resource utilization, and foster long-term social and economic well-being. Eco-strength efficiency is the ratio of compressive strength and embodied carbon of mix proportions as clearly depicted in Eq. 1 . ESE = \(\:\frac{Compressıve\:strength\:\left(28\:days\right)}{Embodıed\:carbon\:proportıon\:mıx}\) …………………..Eq. (1 ) Integrating innovative material and smart mix designs, the building industry can achieve high performance concrete with minimal environmental harm. Figure 18 displays the ESE mixes of materials utilized in this research. Mix 3 (10% SF; 5% SSA; 0% RP) had the highest ESE of 0.22 Mpa/KgCo 2 .m 3 , whereas Mix 4 had the lowest ESE of 0.08 Mpa/KgCo 2 .m 3 . The ESE of other mixes, including mix 1 and 2, was equally higher than that of the control mix. Earlier work from Alnahhal et al., 2018 , Stark et al., 2006 , yielded consistent outcomes. 5. Conclusion The experimental study on the valorization of industrial byproducts in concrete concentrating on synergistic effects of sewage sludge ash and silica fume with recycled plastic fine aggregates yielded significant insights into the performance of modified concrete mixes. The results demonstrated that the incorporation of these materials influenced the fresh, mechanical and durability properties of the concrete in distinct ways: The inclusion of silica fume and sewage sludge ash (mixes 1,2, &3) reduces the slump values indicating a decrease in workability. The effect was more pronounced in mixes containing plastics aggregates (mixes 5,6, &7), suggesting that plastic aggregate further impacted the consistency of the concrete. The incorporation of plastic aggregate significantly reduced the density of the concrete highlighting its potential for light weight applications. On the other hand, mixes containing SF and SSA alone (mixes 1,2&3) displayed minimal changes in density in reference to the control mix. Mixes containing silica fume and sewage sludge ash (mixes 1,2&3) enhanced the compressive strength after 28 days with the highest strength observed in mix 3 (10% SF, 5% SSA). Mix 4 (30% RP) exhibited the lowest strength but the combination with silica fume and sewage sludge ash mitigated the effect as seen in mix 7 (10% SF, 5% SSA, 30% RP) which demonstrated high strength compared to other mixes containing plastic aggregates Comparative pattern was noted for splitting tensile strength where recycled plastic (mixes 4) had a negative impact while SF and SSA (mixes 1,2, &3) enhanced the performance. However, the strength reduction in recycled plastic mixes was somewhat offset by the synergistic effect of silica fume and sewage sludge ash (mixes 5,6, &7) compared to mix 4. Mix 3 (10%SF & 5% SSA) outperformed other mixes with a 3.2% water absorption percentage, due to the pozzolanic reaction of silica fume and sewage sludge ash. Mix 4 (30% RP) showed the highest water absorption percentage (8.2%) due to improper integration of plastic and fine aggregate into the cement matrix. The study found that concrete mixes exposed to H2SO4 acid solution diminished strength after 28 days. Sulfate attack, a chemical reaction, shortens concrete's lifespan by interacting with calcium hydroxide and calcium aluminate hydrates. Mix 3 showed the best resistance to acid attack, while mix 4 exhibited the least resistance. The presence of plastic waste in the mix could compromise the concrete's ability to withstand acid and sulfate assaults. To reduce the impact of these attacks, precautions like using SCM can be taken. When compared to the control mix, mix 3 (10% silica fume (SF) + 5% sewage sludge ash (SSA) as cement replacements) had the lowest embodied carbon (EC), lowering it by 13.7%. Similarly, compared to the reference mix, a mixture of 10% SF, 5% SSA, and 30% recycled plastic (RP) reduced EC by 13.3%. The eco-strength efficiency of Mix 3 (10% SF + 5% SSA) was 37.5% greater than that of the traditional OPC mix, demonstrating its excellent balance of environmental advantages and mechanical performance. Concrete's mechanical qualities may not be improved by the use of recycled plastic, but its durability may be, especially when mixed with SCM, depending on the proportion of plastic used. This method helps preserve natural resources like sand and lowers the self-weight of concrete in constructions. Furthermore, recycled plastics may be utilized in a wide range of buildings where toughness is not a crucial consideration, including road medians and sub-bases for highway pavements. In order to provide pervious concrete for ground water recharge through pavement area, plastic blended concrete can be utilized. Therefore, by lowering problems associated with the disposal/ landfills, plastic, SF, and SSA may eventually be a practical substitute for conventional aggregate and cement while also promoting environmental sustainability. Additionally, it will lessen the negative effects on the environment caused by the unsustainable depletion of natural resources to meet the rapidly increasing demand for aggregates. The study demonstrates that RP's lightweight qualities are appropriate for non-structural applications, whereas SF and SSA work in concert to improve concrete performance through combined filler and pozzolanic effects. To increase its utility, further research should enhance RP-cement bonding. The building industry's shift to alternative materials (silica fume, sewage sludge ash, plastic aggregate) shows its dedication to environmentally friendly concrete production methods and sustainability over time. Adopting these substitutes shows a dedication to reducing ecological effects and developing a more environmentally friendly built environment in the future. The building sector is getting nearer to achieving its goals of minimizing adverse environmental consequences as research and development continues, opening the door for a more environmentally friendly construction sector. Recommendation Evaluation of the long-term leaching of concrete combined with SSA. Assess the environmental safety of SSA-concrete by tracking the leaching of heavy metals (such as Pb, Cd, and Cr) during long exposure times (5–10 years). Surface Modification of RP Aggregates by chemical treatment to improve the bonding between the cement paste and recycled plastic aggregate. Examine other durability properties of the blended concrete such as drying shrinkage, freeze and thaw. Declarations Acknowledgments: The authors would like to express their acknowledgment and appreciation to the Department of Civil Engineering at Cyprus International University for all of the technical support provided, CRediT authorship contribution statement: Babatunde olufunso oluwole: writing – original draft, investigation, conceptualization, data curation. Ömer Damdelen : supervision, conceptualization, writing – review &editing. Stephen Babajide Olabimtan : writing – original draft, investigation, conceptualization, data curation. All authors have read and agreed to the published version of the manuscript. Funding : This research received no external funding Conflict of Interest: The authors wish to affirm that this publication has no known conflicts of interest, and there has not been any significant financial support that would have affected the results of this work. 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Mechanism and Performance Control Methods of Sulfate Attack on Concrete: A Review. Materials , 17 (19), 4836–4836. https://doi.org/10.3390/ma17194836 Additional Declarations No competing interests reported. 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16:01:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4451072,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7207003/v1/db345dfb-0734-4427-b30c-c8f7c0844b03.pdf"},{"id":89408902,"identity":"326ecba1-fdc2-4579-941a-4288577f6446","added_by":"auto","created_at":"2025-08-19 15:45:25","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":254240,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.docx","url":"https://assets-eu.researchsquare.com/files/rs-7207003/v1/e259bb44b047b3c856d9a43e.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Valorization of Industrial Byproducts in Concrete: Synergistic Effects of Sewage Sludge Ash and Silica Fume with Recycled Plastic Fine Aggregates","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe manufacturing of cement is the second-biggest industrial producer of carbon dioxide (CO\u003csup\u003e2\u003c/sup\u003e) after the iron and steel sector, accounting for 7% of worldwide CO\u003csup\u003e2\u003c/sup\u003e emissions, based on the International Energy Agency (IEA). According to Benhelal et al., (2013), cement factories are responsible for around 5\u0026ndash;7% of worldwide CO\u003csup\u003e2\u003c/sup\u003e releases; one ton of cement produces 900 kg of CO\u003csup\u003e2\u003c/sup\u003e emissions into the atmosphere. Significant CO\u003csup\u003e2\u003c/sup\u003e emissions are produced by the energy-intensive and extremely heated procedure needed to manufacture cement, and the industry's environmental effect is increased by the widespread use of concrete in building (Zeidabadi et al., \u003cspan citationid=\"CR98\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Consequently, enhancing energy efficiency, minimizing environmental impact, and valorizing waste materials constitute fundamental challenges facing the industry (Uliasz-Bocheńczyk., 2012). There is a lot of research being done to provide environmentally friendly cement alternatives that don't affect the strength and functionality of the concrete. Accordingly, mitigating this challenge calls for systematic approaches to cut emissions in different economic domains while implementing green practices to alleviate environmental impacts (Peters et al., \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2013\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSecond only to water, concrete is the most commonly used material worldwide (Bhardwaj \u0026amp; Kumar., 2017). It is composed of readily available and low-cost materials such as cement, aggregate, and water, making it a fundamental resource in construction. Aggregates, which make up 65\u0026ndash;80% of the volume of concrete, are essential for defining the material's volume stability, strength, durability, workability, and permeability (Faraj et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Large amounts of coarse and fine aggregates must be utilized in the manufacturing of concrete in order to fulfill the requirement for the material worldwide (Spiesz et al., \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Reducing waste buildup can be achieved by integrating waste materials into the manufacturing of concrete. This environmentally friendly method helps address the lack of natural aggregates on building sites while also reducing the negative effects of excessive aggregate mining and landfill dumping (Saikia \u0026amp; De Brito., 2014).\u003c/p\u003e\u003cp\u003ePlastic is a ubiquitous substance and one of the most significant inventions of the 20th century. A significant quantity of waste is produced as a result of manufacturing operations, municipal solid waste, and service businesses (Alaloul et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Massive amounts of plastic garbage are disposed of every day using unsustainable techniques, making it a serious ecological hazard. Landfilling, ocean dumping, and incineration are examples of current disposal methods that have a variety of negative environmental effects, including pollution of the land, harm to marine habitats, and air pollution from burning hazardous pollutants. The plastic recycling sector confronts significant barriers despite growing environmental demands, including: contamination issues, technological limitations in processing, low commercial viability of recycled products, costly operations, inefficient waste management systems, lack of consumer education, and mounting single-use packaging waste (Geyer et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). It is necessary to establish comprehensive solutions that involve cooperation amongst several sectors, including industry, government, and the general public, in order to address these issues and promote successful plastic recycling (Burgess et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wu et al., 2021). One potential strategy is to use plastic to replace aggregate in concrete. This technique allows recovered plastics to be utilized again without losing quality over time, and more significantly, it eliminates the need for virgin building materials. The physical characteristics of plastic, such as its low weight and excellent strength-to-weight ratios, make it a suitable substitute for conventional aggregate materials. Additionally, plastic can increase the durability and resilience of concrete to some kinds of damage, such water intrusion and cracking (Mehta \u0026amp; Monterio., 2014). The incorporation of plastic waste as a partial replacement for conventional aggregates in concrete offers dual benefits of waste reduction and enhanced material performance (Thorneycroft et al., \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Plastic aggregates demonstrate advantageous material properties including superior strength-to-weight characteristics, reduced density, and minimal water absorption - attributes that improve freeze-thaw resistance and durability in harsh environmental conditions (Ruijun et al., \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Additionally, this substitution presents environmental advantages through lower energy requirements in production compared to natural aggregates, thereby reducing the carbon footprint of concrete manufacturing. Fine aggregates were replaced in concrete by Alagusankareswari et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, using 0%, 10%, 20%, and 30% plastic waste aggregates. Substituting 10%, 20%, and 30% fine aggregates resulted in self-weight reductions of around 3.8%, 7.25%, and 10.96%, respectively. According to the experimental findings, mechanical strength and plastic waste substitution % were inversely correlated. As plastic waste replacement rates increased, compressive strength declined by 7.6%, 21.47%, and 26.11%, while tensile strength dropped by 1.67%, 20.98%, and 38.98%. Choi et al., (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) evaluated the fresh and mechanical qualities of concrete made with PET trash from plastic jugs as a fine aggregate alternative. When 75% PET waste plastic was used as a natural fine aggregate substitute, a 21% decrease in compressive strength was observed.\u003c/p\u003e\u003cp\u003eSewage sludge is an outcome of the treatment of wastewater. The removal of sewage sludge generated during sewage processing has long been a major challenge in modern society and cities. The volume of sewage sludge has grown significantly over time due to industrialization and expanding populations, and it is predicted to continue to rise. Attention over the city's surroundings have grown as a result of the substantial volumes of sewage sludge that are building up in wastewater processing facilities and the insufficient area for dumping. Sewage sludge disposal may be divided into three main categories, however there remain a lot of \"unclear segments\" among these clear-cut methods. These disposal methods include using it as fertilizer on agricultural land, disposing of it in the ocean, and landfilling (\u0026Oslash;degaard et al., \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Nowadays, the sludge produced in wastewater treatment facilities is often disposed of by landfilling (Lin et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Due to a lack of landfill places (Chen et al., 2018a) and increasing worries about the spread of diseases to crops and the buildup of heavy metals on cultivatable soils, several nations have rigid rules regarding the disposal of sewage sludge (Commission, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1986\u003c/span\u003e). Modern disposal practices have been linked to environmental problems like air, water, and pollution, according to recent studies (Jamshidi et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Sewage sludge dumping in the water has a negative effect on the marine ecosystem (Chung et al., 2020). This is due the bacteria that are drawn to sewage sludge absorbs a lot of oxygen to destroy the waste, which results in a shortage of oxygen in the area that is essential for marine organisms to survive (Angel, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Sewage processing firms are now financially burdened with getting rid of sewage sludge. 7\u0026nbsp;million metric tons of sewage sludge will be produced yearly in 2020, according to Siti Noorain (2013), with management expenses reaching US\u003cspan\u003e$\u003c/span\u003e 0.33\u0026nbsp;billion yearly. It is not deemed environmentally or economically viable to landfill sewage sludge, dispose of it in the ocean, or use it as fertilizer for the reasons listed above and the rising understanding that it may be recycled instead of disposed of. One of the alternate methods for getting rid of sewage sludge is incineration. The main ingredients of standard cements, such as SiO\u003csub\u003e2\u003c/sub\u003e, CaO, and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, are found in sewage sludge following high temperature incineration (Tenza-abril et al., 2011). Incorporating SSA as an alternative to cement is a sustainable option since it exhibits pozzolanic characteristics which can react with calcium hydroxide forming secondary CSH gel which improves the mechanical and durability characteristics of concrete. This is a sustainable way to lessen the environmental effects and carbon emissions linked to conventional cement manufacture. According to an experimental study done by Monz\u0026oacute; et al., 1999, the compressive strength of cement-based mortar at 40\u0026deg;C after 3 to 28 days of curing is not considerably impacted by replacing 15% or 30% of the cement with SSA. According to studies, 8% SSA by mass inhibited the cement's early hydration while negatively affecting the ductility of ultra-high strength concrete (UHPC). Nevertheless, in the later phases of curing, pozzolanic reactions enhanced. The pore structure of UHPC was shown to be affected by the inclusion of SSA, leading to a reduce in large pore volume and a rise in cumulative pore volume. According to Gu et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), SSA also raised drying and autogenous shrinkage values. Furthermore, it was discovered that adding SSA to the mortar improved its compressive strength and slowed down its rate of water absorption. Another investigation by Tutur et al. (2019) examined the impact on compressive strength of replacing cement with a mixture of rice husk ash (RHA) and sewage sludge ash in different amounts (10%, 20%, 30%, 40%, and 50%). The best impact on compressive strength was found when 10% of the cement was replaced with SSA and RHA. Guo et al. (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) discovered that while adding 10% slag and 10% fly ash enhanced overall effectiveness, adding 30% SSA decreased the mixture's flow rate and compressive strength. According to the research by Nakic et al., 2018, a 10% SSA percentage was able to attain comparable strength after three days of curing, with a little enhancement noted at seven and twenty-eight days of testing. It is recommended to use a modest percentage of SSA (usually 5\u0026ndash;10%) to boost compressive strength because of its pozzolanic activity, which can counteract the rise in porosity caused by the porous characteristics of SSA in the concrete mix (Hassooni \u0026amp; Ethaib., 2020). Improved compressive strength at 28 days of curing compared to a slow strength increase at an early age for the evaluated SSA concrete mixes, according to research by Xia et al., 2023. The author attributed this behavior to the existence of PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e in the SSA, which disintegrates in the mix and prevents the hydration of C3S in cement at an early age, as well as the greater absorption of water for the SSA particles, which would be discharged at older ages in order to promote the hydration process.\u003c/p\u003e\u003cp\u003eThe construction industry has increasingly adopted silica fume as a pozzolanic additive in recent years. When incorporated at optimal percentages, it effectively improves concrete performance in its plastic and cured states boosting cohesion, mechanical strength, permeability, and overall durability. The airborne dissemination of silica fume, a byproduct of the smelting of silicon-based alloys (such as calcium silicon, ferro-chromium, and ferro-manganese), can cause occupational health issues and environmental deterioration. This pozzolanic material serves dual purposes in concrete production: it can replace a portion of cement (often to lower material costs) or act as a supplementary additive to boost key properties in fresh and cured concrete, including its renowned strength-enhancing capability (\u0026zwnj;De la Pr\u0026eacute;contrainte.,1988). Numerous investigations and research projects have taken into account the use of silica fume because of its excellent outcomes. The use of silica fumes as a partial cement substitute improved the workability, mechanical strength, and aggregate interlocking of concrete (Singh et al., \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The effect of silica fume on Concrete's fresh Properties Nematzadeh and Hasan-Nattaj (\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) investigated the slump flow of very durable concrete. Their findings showed that slump decreased as the percentage of concrete that had silica fume replacement increased. According to Wu et al., \u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, ultra-high strength concrete containing silica fume showed a discernible improvement in compressive strength findings at early ages. The study conducted by Rostami and Behfarnia., (2017) showed that increasing silica fume dosage progressively decreases concrete's water absorption capacity. Test results indicated that mixes containing 5%, 10%, and 15% silica fume exhibited 5.97%, 9.70%, and 13.06% lower water absorption than conventional concrete. Studies show that incorporating 5\u0026ndash;15% silica fume as a cement replacement yields the highest compressive strength at 28 days. The improvement stems from silica fume's pozzolanic activity - it reacts with calcium hydroxide from cement hydration to generate more C-S-H gel, which strengthens the concrete matrix (Mohan \u0026amp; Hayat., 2021).\u003c/p\u003e\u003cp\u003eCritical gaps still exist despite advancements in waste-valorized concrete: (1) combined SSA-SF-RP systems have not been investigated; (2) there is a lack of durability data for concrete, especially with regard to sulfate resistance; and (3) there is no framework in place to balance the environmental benefits and mechanical performance of these cement systems. This research addresses these gaps. Sustainable building has become an essential component of civilization due to the advancement of technology. Concrete development is therefore required due to the growing need for stronger, more resilient, and long-lasting constructions. In order to improve the sustainability of concrete, this study intends to experimentally examine the effects of partially substituting cement and sand with different amounts of silica fume, sewage sludge ash, and recycled plastic on the mechanical, physical, and durability properties of concrete.\u003c/p\u003e"},{"header":"2. Materials and Experimental Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Raw Materials\u003c/h2\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003e2.1.1 Cement, Mixing Water and Admixtures\u003c/h2\u003e\u003cp\u003eThe study employed concrete mixtures prepared using CEM II type cement. The ASTM C150/C150M-21 requirements can be applied with this specific type of cement. To achieve a minimum compressive strength of 42.5 megapascals (MPa) over a 28-day curing period, the concrete was formulated using 42.5-grade cement in compliance with ASTM rules. As the mixing water for the research, regular tap water with a pH between 6.5 and 7 was utilized. The criteria of ASTM C1602/C1602M-18 were tightly followed to guarantee that all concrete mixes and the subsequent curing method were free of acids, greases, and organic impurities. A high-range water reducer called a superplasticizer was added to the mixing water in order to account for the low water-to-binder ratio. The goal of this modification was to increase the compaction process and workability. In particular, the study used a glenium-based superplasticizer.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.1.2 Fine aggregate\u003c/h2\u003e\u003cp\u003eParticles that pass through a 4.75 mm sieve are referred to as fine aggregate. The fine aggregate selected was crushed limestone, which complies with ASTM C33/C33M-18 requirements. The sand was produced in accordance with ASTM C128-17a requirements, guaranteeing that it maintained a saturated surface dry state in order to limit water absorption during mixing. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the particle size distribution of the natural aggregate utilized, and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e provides more details regarding the properties of the sand.\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\u003eSand properties\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\u003ePROPERTIES\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePARAMETERS\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eASTM\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater Absorption (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC128-15\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\u003e2.630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC128-15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFineness Modulus\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC33/C33M-18\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\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC566-19\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLoss Bulk Density (kg/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1576\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC29/C29M-17a\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCompact Bulk Density (Kg/m\u003csup\u003e3)\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1728\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eC29/C29M-17a\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.1.3 Coarse aggregate\u003c/h2\u003e\u003cp\u003eThe size variation of the coarse particles employed can have a major impact on the qualities of concrete, such as its strength and workability. The particle size distribution of coarse aggregates in concrete mixes may be precisely determined and controlled with the use of standards like ASTM C136M-14 and C33M-16. These guidelines guarantee that the aggregates fulfill certain requirements, improving the uniformity and performance of the final concrete.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.1.4 Silica fume\u003c/h2\u003e\u003cp\u003eThe smelting of silicon and ferrosilicon produces silica fume (SF), also known as microsilica, condensed silica fume, volatilized silica, and silica dust. It is composed of extremely thin vitreous particles and has a surface area of 13,000 to 30,000 m\u0026sup2;/kg. It is available in white or gray colors. The high proportion of silica and its high fineness make silica fume an extremely effective pozzolanic mixture. Figures\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e \u0026amp; \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the physical appearance and SEM of silica fume utilized in the study. The chemical composition of silica fume is depicted in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\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\u003eChemical composition of silica fume\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChemical Compound\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSilica fume\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCaO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e92.26\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.89\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe2O3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.97\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eK\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTio\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.01\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=\"Sec8\" class=\"Section3\"\u003e\u003ch2\u003e2.1.5 Recycled plastic\u003c/h2\u003e\u003cp\u003eA mixture of post-consumer polyvinyl chloride (PVC), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE) plastics was used to partially substitute fine aggregate in the manufacturing of concrete. The plastics were crushed into tiny pellets that ranged in size from 300 \u0026micro;m to a maximum average size of 3.0 mm. A nearby recycling plant in the Lefkosa area of the Turkish Republic of North Cyprus (TRNC) provided the plastic pellets shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\u003ch2\u003e2.1.6 Sewage Sludge Ash\u003c/h2\u003e\u003cp\u003eSludge was taken from the waste water treatment plants disposal facility in Haspolat Nicosia. North Cyprus. Pyrolysis was used to treat sewage sludge ash in a furnace for two hours at 850\u0026deg;C. The ash from sewage sludge was then left to cool gradually before being ground with the Los Angeles machine to particles that passed through 75 \u0026micro;m sieves. Its specific gravity and water absorption were 2.72 and 0.86, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\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\u003eChemical composition of sewage sludge ash\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChemical Compound\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSEWAGE SLUDGE ASH\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCaO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e24.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e9.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe2O3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSO3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMGO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLOI\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.88\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ep\u003csub\u003e2\u003c/sub\u003e0\u003csup\u003e5\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e24.1\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\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Experimental Methodology\u003c/h2\u003e\u003cp\u003eIn addition to a reference mix, eight distinct concrete mixes were made, each with a different amount of silica fume and sewage sludge ash added to partially replace cement and fine aggregate replaced with recycled plastic. In order to maintain a constant water-to-binder ratio of 0.50, superplasticizer was applied evenly. This study looks at the feasibility of employing these waste products in the production of concrete, as well as promoting sustainable construction practices and reducing the environmental impact of conventional materials.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e2.2.1 Mix Design\u003c/h2\u003e\u003cp\u003eIdentifying the amounts and ratios of key ingredients in concrete mixtures to provide the required workability, characteristic strength, and peculiar material qualities is the fundamental definition of design mix. In this work, concrete made from silica fume, Sewage sludge ash, and recycled plastic was constructed utilizing eight different combinations and the experimental approach. To determine the characteristics and ratios of the mixtures, which include the sand-to-binder (cement, silica fume, Sewage sludge ash) and water-to-binder ratios, the first step was to create experimental mixes. The design of the concrete mix encompassing 5% SSA, 10% SF and 30% RP is based on the combination of the efficiency of the material, sustainability objectives and practical constraints. Prior to earlier researches increasing the doses of SSA culminates into decreased early strength, and silica fume over 10% increases cost and 30% Rp was adopted as a threshold which serves as an alternative to sand without significantly compromising the mechanical characteristics. The modified SP doses and the % mix design are displayed in Tables\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\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\u003eDescription of the Concrete mixes\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\u003eMIX ID\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDESCRIPTION\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eControl Mix\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% Silica fume, 0% SSA, 0% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% Silica fume, 5% SSA, 0% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% Silica fume, 5% SSA, 0% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% Silica fume, 0% SSA, 30% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% Silica fume, 0% SSA, 30% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% Silica fume, 5% SSA, 30% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% Silica fume, 5% SSA, 30% Recycled plastic\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"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\u003eMix design of the Concrete mixes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"12\"\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=\"char\" char=\".\" 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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLABEL\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMIXES\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eW/C\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eW\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSF\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eSSA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eFA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eRP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c11\" namest=\"c10\"\u003e\u003cp\u003eCA kg/m3\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eSP\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e10mm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e20mm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003ekg/m3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% SF; 0% SSA; 0% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e420\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e891\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10%SF; 0% SSA; 0% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e378\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e891\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% SF; 5% SSA; 0% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e399\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e891\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% SF; 5% SSA; 0% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e357\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e891\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% SF; 0% SSA; 30% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e420\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e623.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e267.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% SF; 0% SSA; 30% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e378\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e623.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e267.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0% SF; 5% SSA; 30% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e399\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e623.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e267.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMIX 7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10% SF; 5% SSA; 30% RP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e210\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e357\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e623.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e267.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e363\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003e726\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"12\"\u003e\u003cb\u003eNB: w/c: water to cement ratio, W: Water, C: Cement, SF: Silica fume, SSA: Sewage Sludge Ash, F.A: Fine aggregate, RP: Recycled plastic, CA: Coarse aggregate, SP: Superplasticizer\u003c/b\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e2.2.2 Casting procedure\u003c/h2\u003e\u003cp\u003eAll of the concrete blends were made according to ASTM C305-20 guidelines. The concrete mixer was used to generate each test sample. For one minute, the coarse aggregate, 50% water, and 50% cement are well mixed. Then, the remaining 50% cement, 25% water, fine aggregate, and superplasticizer are added, and the mixture is combined for three minutes. The remaining 25% water was added last, and the mixture was stirred for three more minutes. The specimens were put into cube molds (100 mm x 100 mm x 100 mm) after the mixing procedure was complete.\u003c/p\u003e\u003cp\u003eThe specimens were subjected to a number of tests to ascertain their characteristics in both fresh and hardened stages, such as the acid attack test, compressive strength, splitting tensile strength, water absorption, and dry density. Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e provides an overview of the tests conducted for this investigation.\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\u003eSummary of experiments conducted for this study.\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\u003eTest\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCode/ standards\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSpecimen\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCompressive strength\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eASTM C349-18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100x100x100 mm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSplitting Tensile Strength\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eASTM C496-96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100x100x100 mm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater Absorption\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eASTM C1585-20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100x100x100 mm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAcid Attack Test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eASTM C267\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100x100x100 mm\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\u003c/div\u003e"},{"header":"3 Result and Discussion","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Workability\u003c/h2\u003e\u003cp\u003eThe slump test evaluates concrete's workability, which is its capacity to flow uniformly while maintaining cohesion. Numerous factors, such as the type, quantity, and characteristics of the ingredients in the combination, affect the consistency and handling process of concrete. The properties of novel concrete may be examined by substituting some of the traditional concrete elements with silica fume, sewage sludge ash, and recycled plastic. Assessing the effects of these replacements on the consistency and workability of the mixture is made easier by the slump test results. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e shows the outcomes of the slump test, which evaluates how workable and consistent fresh concrete is.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe slump measurements across the different mixes fell within the range of 33 mm to 58 mm, with the control mix recording the highest value. When compared to the control mix, mixes 1 through 7 exhibited lower slump values, decreasing by 27%, 21%, 31%, 17%, 34%, 38%, and 43%, respectively with mix 7 showing the least slump. The reason for this slump decreases is due to the incorporation of the additives utilized. Silica fume requires more water for efficient lubrication due to its smaller particles and larger surface area than OPC making the concrete mixture less workable and more rigid as a result. Nedunuri et al., (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), Mohan \u0026amp; Mini., 2018, also reported reduced workability as a result of silica fume's higher water consumption because of its large surface area and ultrafine particles, which is consistent with our findings.\u003c/p\u003e\u003cp\u003eSSA's high surface area and irregular particle shape, which both encourage more water absorption at the particle interface, are also part of reasons why introducing it to cementitious systems decreases workability. The porous structure enhances water absorption capacity, while the irregular particle geometry promotes particle rearrangement within the mortar matrix, creating numerous void spaces (Lin et al., 2008). Additionally, SSA contains a greater level of P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e, which results in a very hygroscopic matrix (Lawrence., 1998). The research outcomes of Gu et al., (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) aligned with these observations. The addition of recycled plastic to concrete also contributes to reduced workability and the effect occurs through two mechanisms: First, flow is impeded and internal friction is produced by the plastic particles' uneven shapes and sharp edges. Secondly, because plastics are water-repellent, air bubbles develop at the surface of the particles, creating gaps at the plastic-cement interface. Increasing the amount of RP added to the combination intensifies both effects (Z\u0026aacute;lesk\u0026aacute; et al., \u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Tota-Maharaj et al., 2022, reached analogous finding in their work.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Compressive strength\u003c/h2\u003e\u003cp\u003eOver the course of the 7, 14 and 28day curing periods, the different mixes showed differing strength improvements as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, which was indicative of the combination\u0026rsquo;s gradual hydration and pozzolanic reactions. The cementitious ingredients continued to react as the curing period rose, resulting in the development of more calcium silicate hydrate (C-S-H) gel and greater compressive strength. Initial hydration was the main cause of the early strength at 7 days, although continuing hydration and subsequent pozzolanic reactions, especially in mixes with additional cementitious elements like silica fume and sewage sludge ash, had an impact on the later strength growth (14 and 28 days). This pattern demonstrates how extended curing greatly enhances the set material's microstructure and durability.\u003c/p\u003e\u003cp\u003eAt 7 days of curing, the control mix achieved the highest compressive strength among all mixes. Although Mix 3 (10%SF \u0026amp; 5%SSA) demonstrated superior strength compared to other modified mixes, it still exhibited lower early-age strength than the control. This can be attributed to the delayed pozzolanic reaction of silica fume and sewage sludge ash (SSA), which results in slower strength development at early stages. Similar findings were reported by Al Shanti et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e and Khawal and Sangwai., 2019, who observed that SSA blended concrete mixes experienced slower initial strength gain due to the reduced cement content, which hindered early hydration reactions. Since pozzolanic materials progressively react with calcium hydroxide to generate more cementitious compounds over time, the delayed strength growth is typical of these materials. Although the SSA and SF mixes may have a somewhat lower initial strength increase, strength rate gain improves during the 14 \u0026amp;28 day curing period (Gu et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In comparison to the control mix, mix 2, which included 5% SSA, likewise shown decreased early-age strength. The high-water absorption of SSA particles, which subsequently liberated moisture to promote hydration, was associated with this activity. Furthermore, the early hydration of C₃S in the cement was impeded by the existence of PO₄\u0026sup3;⁻ in the SSA dispersed within the mixture (Rutkowska et al., \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eMix 3 (10% SF \u0026amp; 5% SSA) demonstrated the highest compressive strength after 28 days of curing, showing a 18% strength improvement over the control mix. The addition of silica fume (SF) enhanced the compressive strength due to its fine particle size and strong pozzolanic reactivity. The calcium hydroxide released during cement hydration reacted with the reactive silica, forming additional CSH gel that densified the cement matrix, thereby increasing the concrete's strength. Shi et al., \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, research yielded comparable conclusions. In comparison to the control mix, mix 1 (10% SF) and Mix 2 (5% SSA) demonstrated strength improvements of 9% and 5%, respectively, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. Similar conclusions were drawn by Mohammed et al., 2024, in their research. Nevertheless, mix 3 was superior compare to both mixes. This implies that SF performs better as a cement replacement when combined with SSA, leading to increased compressive strength and the production of more ecologically friendly and sustainable building materials.\u003c/p\u003e\u003cp\u003eMix 4 exhibited the lowest strength among all mixes, with a 49% reduction compared to the control mix. This decline in compressive strength is likely attributed to the smooth surface of the plastic waste, leading to weak bonding between the plastic and the cement paste (Ullah et al., 2022; Almeshal et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Also, the recycled plastic concrete is weakened by the formation of a thin water layer around the hydrophobic plastic granules (Pezzi et al., \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Concrete strength is also greatly influenced by the plastic waste elastic modulus. The inclusion of plastic waste with a high elastic modulus, lowers the concrete's compressive strength. In contrast to plastic waste with a greater elastic modulus, like PET aggregates, plastic waste with a lower elastic modulus, like EPA aggregates, results in a more significant reduction in compressive strength (Almeshal et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The particle shape of the aggregate can compromise the compressive strength of concrete, Gu and Ozbakkaloglu found that concrete mixtures with irregularly shaped plastic waste aggregate experience a greater decrease in compressive strength than concrete mixtures with consistently shaped plastic waste aggregate. Although mixes 5,6 and 7 showed lower strength than the control mix, their performance was better than mix 4 due to the pozzolanic activity of the supplementary cementitious material (silica fume and sewage sludge ash) explained earlier. Tanli et al., 2022, Ullah et al., 2022, all arrived at similar conclusion in their respective researches.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Splitting Tensile Strength\u003c/h2\u003e\u003cp\u003eTo evaluate a concrete specimen's tolerance to elongation, the splitting tensile strength test is usually performed. With a 6% increase in tensile strength above the control mix which mirrored the trend seen in the compressive strength, mix 3 (10% SF \u0026amp; 5% SSA) had the best performance as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e. The greater tensile strength values can be attributed to the same factor as were previously discussed for compressive strength. In comparison to the reference mix, mix 4 has the lowest tensile strength. Higher porosity, the lightweight characteristic of plastic waste aggregates, and the poor binding between the cement paste and plastic waste aggregate are some of the reasons for this decrease in tensile strength when utilizing plastic waste (Ali et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Ullah et al.,2021). Plastic aggregate's smooth texture causes poor adhesion or bonding to form between it and cement paste, which reduces strength (Akinyele \u0026amp; Ajede., 2018). Also, the reduced density, stiffness, unit weight of plastic aggregate relative to fine aggregate culminates to high stress zones promoting damage spread accounting for strength reduction (Ahirwar et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe majority of plastic waste, however, is not removed and stays embedded in the concrete sample, as demonstrated by the concrete's fracture surface in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e. Because plastics are hydrophobic, their usage in concrete reduces the adhesive strength between them and the cement paste, which results in a reduction in tensile strength (Saikia et al., 2012). Danish \u0026amp; Ozbakkaloglu., 2023, arrived at similar conclusion in their studies.\u003c/p\u003e\u003cp\u003eAlthough they exhibited greater strength than mix 4, mixes 5, 6, and 7 also showed less strength than the control mixes. Concrete that contains silica fume and sewage sludge ash, together with 30% plastic waste replacement (mix 7), exhibits a steady increase in tensile strength. Because silica fume and sewage sludge ash are highly reactive and encourage the production of hydration products like calcium silicate hydrate (C-S-H) gel, as well as their filler action in improving densification, this rise in tensile strength may be attributed to them.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Density\u003c/h2\u003e\u003cp\u003eThe densities of the various combinations and the effects of adding silica fume and sewage sludge ash as cement substitutes and plastic aggregates as fine aggregate replacement on concrete density are contrasted in the graph in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e. Mixes 1(10% SF), mix 2 (5% SSA) and mix 3 (10%SF, 5% SSA), exhibited density values comparable to the control mix owing to the densifying filler effect of SF and SSA particles in the cement matrix. Significant decrease in density was observed in mixes (4\u0026ndash;7), compared to the control mix with mix 4 exhibiting 20% decrease, mix 5,6 \u0026amp;7 showing 21%, 21.05% \u0026amp; 20.42% density decrease in respect to the control mix. This is due to plastic low density and smooth sharp-edged characteristics that increase air content and decrease the dry density (Akinyele et al., 2018; Saikia et al., 2014; Colangelo et al., 2016). Another reason for the decrease is that plastic has a lower specific gravity than natural fine aggregate (Sheelan et al., 2019). Because of the decreased concrete density, the structural member's deadweight is decreased. Thus, using recycled plastic in the concrete system might be viewed as beneficial. Numerous experts concur that Yong-Woo Choi (2005) (YW. Choi et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) and Aldahdooh MAA (2018) found that plastics have a lower density, which causes their density to drop.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e3.5 Water Absorption\u003c/h2\u003e\u003cp\u003eThe durability of concrete can be evaluated through water absorption tests, as lower water absorption culminates to greater durability compared to higher water absorption which compromises the durability characteristics of concrete. Figure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e clearly depicts the results of the water absorption test for the concrete mixes. Mix 3 (10%SF \u0026amp; 5% SSA) exhibited the best performance with a 33% decrease in water absorption compared to the control mix. The pozzolanic reaction of silica fume which decreased the concrete samples surface porosity, is responsible for this improvement. Another benefit is attributed to the pozzolanic activity of sewage sludge ash, which facilitated in the refinement of the microstructure, creating a denser cement matrix that prevented water penetration. The incorporation of silica fume and sewage sludge ash increased the specimen\u0026rsquo;s resistance to water penetration by decreasing their permeability when used in concrete. In situations where concrete must be water resistant, this property is essential.\u003c/p\u003e\u003cp\u003eMix 2 (10% SF) and mix 3 (5% SSA) displayed favorable water absorption properties with a 27% and 15% decrease in water absorption compared to the control mix. The specific surface area of silica fume which occupies the voids as well as high silica content which reacts with the calcium hydroxide forming additional CSH gel which improves the microstructure are responsible for the prevention of water permeating into the specimen. The porosity of SSA blended concrete is influenced by two factors, the refinement of the pore structure attributed to its pozzolanic reaction (Chakraborty et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), and the synthesis of ettringite (Aft) which may increase porosity culminating into high water absorption (Gu et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Hamada et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Danish \u0026amp; Ozbakkaloglu., 2023, reached consistent conclusions in their respective researches. In comparison to the control mix, mix 4 (30% RP) showed the highest water absorption percentage with a 42% increase. This is due to the plastic and fine aggregate improper integration into the cement matrix which exacerbated the porosity of the concrete (Saikia.,2013). The evaporation of excess water surrounding hydrophobic plastic waste aggregate, the rise in porosity in concrete caused by plastic aggregate, and the weak ITZ close to plastic particles as a result of a poor bond between the binder matrix and plastic waste aggregate could be the causes of the higher absorbing capacity in comparison to the control. Concrete using plastic aggregate showed a greater absorption percentage than conventional concrete, according to Albano et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2009\u003c/span\u003e. On top of that, the water absorption rises when the size of the plastic particles, the amount of plastic aggregate, and the w/c ratio all increase. Raju et al. (\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) showed outcomes that were comparable.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003e3.6 Exposure to Acid Attack\u003c/h2\u003e\u003cp\u003eThe findings, which are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e, showed that various concrete mixes diminished strength after 28 days of curing in an H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e acid solution. All samples demonstrated reduced strength when exposed to the sulfuric solutions. Comparing mixes 1\u0026ndash;3 to control mix, the control mix showed the least residual strength. Concrete that comes into contact with sulfate-rich environments, such as soil or water, experiences a chemical reaction known as \"sulfate attack,\" which shortens its lifespan. Sulfate ions enter the concrete and interact with calcium hydroxide and calcium aluminate hydrates, which are byproducts of Portland cement hydration. Ettringite, a chemical result with significant expansion and internal tension, is the outcome of this. Additionally, sulphates degrade and reduce the cohesiveness of concrete by destabilizing calcium silicate hydrate (C-S-H) (Zhang et al., \u003cspan citationid=\"CR99\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Mix 3 showed the best resistance to acid attack, like wise mixes 1 and 2. SF's strong pozzolanic response primarily influences the enhancement of paste microstructure and increases resistance to aggressive assaults such surface scaling. Weak microstructural regions and the production of additional CSH gels are decreased by this improvement.\u003c/p\u003e\u003cp\u003eComparing mixes 4\u0026ndash;7, mix 4 exhibited the least resistant to sulfuric acid. There might not be a strong chemical bond between the cementitious matrix and plastic waste particles. The entire chemical makeup of the concrete may be impacted and the hydration process may be hampered if plastic waste is included in the mix (Asokan et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). The concrete's ability to withstand acid and sulfate assaults may be compromised by this interference. Since plastics are non-polar, they generally resist chemical reactions with acids. However, the weak bond between the plastic aggregate and cement paste increases the porosity of the concrete. This porous structure allows sulfate solutions to penetrate reacting with the products of hydration in the cement matrix. As a result, expansive compounds like gypsum and ettringite form creating internal pressure. Since concrete lack sufficient space to accommodate these expanding products crack develop, further compromising its durability. Other precautions can be taken to lessen the impact of sulfate and acid assaults while employing plastic waste aggregates like utilizing SCM. For instance, mix 7 exhibited more resistance to acid attack compared to mix 4. Figure\u0026nbsp;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e16\u003c/span\u003e provides a visual representation of the examination of the materials subjected to sulfuric acid, clearly showing the deterioration of the samples and the damaging impact of the sulfuric acid assault on their surface. In all mixes, white areas were seen on the concrete's surface after 28 days. Gypsum and ettringite may have formed as white patches on the surface as a result of the sulphate solution's reaction with hydration products. The concrete sample' corners and edges showed signs of degradation. These examples unequivocally demonstrate the harm caused by the materials engagement with the corrosive properties of sulfuric acid resistance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Sustainability Assessment","content":"\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Embodied Carbon\u003c/h2\u003e\u003cp\u003eThis section covers the eCO2 emission evaluations calculations, and the performance of Eco strength efficiency evaluations of the material used, as to ascertain the sustainability of the SF, SSA and RP used as cement and fine-aggregate alternative. This focused on comparing the viability of achieving sustainable delivery of mixes containing different percentages of SF, SSA and RP with the control group, consisting of traditional concrete mixes. Due to the loss of natural resources caused by urbanization and industrialization, which intensifies global warming, researchers from all over the world are taking sustainable development into consideration. Since the concrete industry uses a lot of energy and natural resources, its greenhouse gas emissions have expanded dramatically. The mix proportion's embodied carbon is calculated with the use of existing research. Embodied carbon factors for all of the materials used to prepare concrete were extracted from the literature, and the embodied carbon of each percentage was calculated using those embedded carbon factors. Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e displays each material's EC factors.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eMaterial's EC factors.\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\u003eMaterıals\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEmbodied carbon factors (Kg.CO2/Kg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRef.\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCollins, (2010)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSilica Fume\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.024\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eThilakarathna et al., (2020)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSewage Sludge Ash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.0513\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGalabada et al., (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRecycled Plastics\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.0051\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eHammond\u0026amp;Jones, (2008)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003efine aggregate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.0139\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTurner and Collins, (2013)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ecoarse aggregate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.0043\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAlnahhal et al., (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWater\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eJones et al., (2011)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSuperplasticizer\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKumar et al., (2021)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe embodied carbon of the concrete mixes used in the study is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e17\u003c/span\u003e. The lowest amount of embodied carbon, around 311.05 kg CO\u003csub\u003e2\u003c/sub\u003e/kg, was found in Mix 7. The fact that 30% RP has low embodied carbon in comparison to fine aggregate and 5% SSA 10%SF has very low embodied carbon in comparison to cement makes this clear. There was a decrease in CO\u003csub\u003e2\u003c/sub\u003e emissions once SCMs were added, and the substitution of plastic for fine aggregate also contributed to the decreased embodied carbon. Comparing mix 4 (30% RP) to the control mix, the embodied carbon was lower. This happened because RP was only used to replace the fine aggregates in the mix, not the cement component, which was not replaced with any other material. By reducing the quantity of plastic trash produced, using it in construction offers the benefit of reducing material costs while also taking sustainability into consideration. The rest mixes all showed reduced embodied carbon with control mix exhibiting the maximum embodied carbon of about 362.97 Kg.CO\u003csub\u003e2\u003c/sub\u003e/Kg. Zada et al., 2025, Kumar et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2022\u003c/span\u003e demonstrated sımılar conclusions ın theır research.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Eco-strength Efficiency\u003c/h2\u003e\u003cp\u003eDespite being the most prevalent building materials in the world, the manufacture of concrete massively enhances emission of carbon and resources depletion. The optimization of both the environmental sustainability and the mechanical properties is termed eco strength efficiency in concrete. Eco-strength efficiency promotes sustainable construction, which attempts to lessen environmental effects, minimize resource utilization, and foster long-term social and economic well-being. Eco-strength efficiency is the ratio of compressive strength and embodied carbon of mix proportions as clearly depicted in \u003cb\u003eEq.\u0026nbsp;1\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003eESE =\u003c/b\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{Compressıve\\:strength\\:\\left(28\\:days\\right)}{Embodıed\\:carbon\\:proportıon\\:mıx}\\)\u003c/span\u003e\u003c/span\u003e\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;..Eq.\u0026nbsp;(1\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e\u003cp\u003eIntegrating innovative material and smart mix designs, the building industry can achieve high performance concrete with minimal environmental harm. Figure\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e18\u003c/span\u003e displays the ESE mixes of materials utilized in this research. Mix 3 (10% SF; 5% SSA; 0% RP) had the highest ESE of 0.22 Mpa/KgCo\u003csup\u003e2\u003c/sup\u003e.m\u003csup\u003e3\u003c/sup\u003e, whereas Mix 4 had the lowest ESE of 0.08 Mpa/KgCo\u003csup\u003e2\u003c/sup\u003e.m\u003csup\u003e3\u003c/sup\u003e. The ESE of other mixes, including mix 1 and 2, was equally higher than that of the control mix. Earlier work from Alnahhal et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2018\u003c/span\u003e, Stark et al., \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, yielded consistent outcomes.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThe experimental study on the valorization of industrial byproducts in concrete concentrating on synergistic effects of sewage sludge ash and silica fume with recycled plastic fine aggregates yielded significant insights into the performance of modified concrete mixes. The results demonstrated that the incorporation of these materials influenced the fresh, mechanical and durability properties of the concrete in distinct ways:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe inclusion of silica fume and sewage sludge ash (mixes 1,2, \u0026amp;3) reduces the slump values indicating a decrease in workability. The effect was more pronounced in mixes containing plastics aggregates (mixes 5,6, \u0026amp;7), suggesting that plastic aggregate further impacted the consistency of the concrete.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe incorporation of plastic aggregate significantly reduced the density of the concrete highlighting its potential for light weight applications. On the other hand, mixes containing SF and SSA alone (mixes 1,2\u0026amp;3) displayed minimal changes in density in reference to the control mix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMixes containing silica fume and sewage sludge ash (mixes 1,2\u0026amp;3) enhanced the compressive strength after 28 days with the highest strength observed in mix 3 (10% SF, 5% SSA). Mix 4 (30% RP) exhibited the lowest strength but the combination with silica fume and sewage sludge ash mitigated the effect as seen in mix 7 (10% SF, 5% SSA, 30% RP) which demonstrated high strength compared to other mixes containing plastic aggregates\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eComparative pattern was noted for splitting tensile strength where recycled plastic (mixes 4) had a negative impact while SF and SSA (mixes 1,2, \u0026amp;3) enhanced the performance. However, the strength reduction in recycled plastic mixes was somewhat offset by the synergistic effect of silica fume and sewage sludge ash (mixes 5,6, \u0026amp;7) compared to mix 4.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMix 3 (10%SF \u0026amp; 5% SSA) outperformed other mixes with a 3.2% water absorption percentage, due to the pozzolanic reaction of silica fume and sewage sludge ash. Mix 4 (30% RP) showed the highest water absorption percentage (8.2%) due to improper integration of plastic and fine aggregate into the cement matrix.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe study found that concrete mixes exposed to H2SO4 acid solution diminished strength after 28 days. Sulfate attack, a chemical reaction, shortens concrete's lifespan by interacting with calcium hydroxide and calcium aluminate hydrates. Mix 3 showed the best resistance to acid attack, while mix 4 exhibited the least resistance. The presence of plastic waste in the mix could compromise the concrete's ability to withstand acid and sulfate assaults. To reduce the impact of these attacks, precautions like using SCM can be taken.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eWhen compared to the control mix, mix 3 (10% silica fume (SF)\u0026thinsp;+\u0026thinsp;5% sewage sludge ash (SSA) as cement replacements) had the lowest embodied carbon (EC), lowering it by 13.7%. Similarly, compared to the reference mix, a mixture of 10% SF, 5% SSA, and 30% recycled plastic (RP) reduced EC by 13.3%.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe eco-strength efficiency of Mix 3 (10% SF\u0026thinsp;+\u0026thinsp;5% SSA) was 37.5% greater than that of the traditional OPC mix, demonstrating its excellent balance of environmental advantages and mechanical performance.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eConcrete's mechanical qualities may not be improved by the use of recycled plastic, but its durability may be, especially when mixed with SCM, depending on the proportion of plastic used. This method helps preserve natural resources like sand and lowers the self-weight of concrete in constructions. Furthermore, recycled plastics may be utilized in a wide range of buildings where toughness is not a crucial consideration, including road medians and sub-bases for highway pavements. In order to provide pervious concrete for ground water recharge through pavement area, plastic blended concrete can be utilized. Therefore, by lowering problems associated with the disposal/ landfills, plastic, SF, and SSA may eventually be a practical substitute for conventional aggregate and cement while also promoting environmental sustainability. Additionally, it will lessen the negative effects on the environment caused by the unsustainable depletion of natural resources to meet the rapidly increasing demand for aggregates. The study demonstrates that RP's lightweight qualities are appropriate for non-structural applications, whereas SF and SSA work in concert to improve concrete performance through combined filler and pozzolanic effects. To increase its utility, further research should enhance RP-cement bonding.\u003c/p\u003e\u003cp\u003eThe building industry's shift to alternative materials (silica fume, sewage sludge ash, plastic aggregate) shows its dedication to environmentally friendly concrete production methods and sustainability over time. Adopting these substitutes shows a dedication to reducing ecological effects and developing a more environmentally friendly built environment in the future. The building sector is getting nearer to achieving its goals of minimizing adverse environmental consequences as research and development continues, opening the door for a more environmentally friendly construction sector.\u003c/p\u003e\u003cp\u003e\u003cb\u003eRecommendation\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eEvaluation of the long-term leaching of concrete combined with SSA. Assess the environmental safety of SSA-concrete by tracking the leaching of heavy metals (such as Pb, Cd, and Cr) during long exposure times (5\u0026ndash;10 years).\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSurface Modification of RP Aggregates by chemical treatment to improve the bonding between the cement paste and recycled plastic aggregate.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eExamine other durability properties of the blended concrete such as drying shrinkage, freeze and thaw.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to express their acknowledgment and appreciation to the Department of Civil Engineering at Cyprus International University for all of the technical support provided,\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBabatunde olufunso oluwole:\u003c/strong\u003e writing – original draft, investigation, conceptualization, data curation.\u0026nbsp;\u003cstrong\u003eÖmer Damdelen\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;:\u003c/strong\u003e supervision, conceptualization, writing – review \u0026amp;editing. \u003cstrong\u003eStephen Babajide Olabimtan\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e writing – original draft, investigation, conceptualization, data curation. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eThis research received no external funding\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors wish to affirm that this publication has no known conflicts of interest, and there has not been any significant financial support that would have affected the results of this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate Declaration\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Number:\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e: Not applicable\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary Information:\u003c/strong\u003e not applicable\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval:\u003c/strong\u003e not applicable\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAdeleke, B. 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Mater. 2018, 181, 301\u0026ndash;308.\u003c/li\u003e\n\u003cli\u003eZhang, C., Li, J., Yu, M., Lu, Y., \u0026amp; Liu, S. (2024). Mechanism and Performance Control Methods of Sulfate Attack on Concrete: A Review. \u003cem\u003eMaterials\u003c/em\u003e, \u003cem\u003e17\u003c/em\u003e(19), 4836\u0026ndash;4836. https://doi.org/10.3390/ma17194836\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":false,"email":"","identity":"discover-concrete-and-cement","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Discover Concrete and Cement","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"Unsupported Journal","inReviewEnabled":false,"inReviewRevisionsEnabled":false},"keywords":"Durability, Industrial by-product, Mechanical Property, Supplementary Cementitious Material, Sustainability, Sustainable concrete","lastPublishedDoi":"10.21203/rs.3.rs-7207003/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7207003/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePlastics are inexpensive, lightweight, adaptable, and easily available. The manufacture of plastic has increased dramatically over the past 50 years, and its use has become an essential part of our daily life. Consequently, the production of plastic-related waste is rising, which threatens the ecosystem. Sewage sludge ash (SSA) is an inevitable waste product of wastewater treatment, and it poses a serious danger of contamination due to its high concentration of heavy metals. Various strategies are put forth globally to dispose of SSA in a sustainable and safe manner. One such method is using SSA, together with other industrial by products, to substitute cement in the creation of cementitious composites. This study explores the use of recycled plastic, sewage sludge ash, and silica fume as cement and fine aggregate substitutes. Using these materials, the study assesses the mechanical properties, workability, durability and environmental assessment of concrete, highlighting their sustainability and potential to reduce waste in the construction sector. A total of eight mixes were prepared, incorporating varying proportions of sewage sludge ash (SSA) and silica fume (SF) as partial replacements for cement, along with recycled plastic as a substitute for fine aggregate in concrete. The control mix demonstrated the best slump value among all mixes. However, mix 3 (containing 10% SF and 5% SSA) achieved the highest compressive and splitting tensile strength with an 18% and 6% increase in strength compared to the control mix after 28 days curing period. Additionally, mix 3 showed superior performance in water absorption and acid resistance tests. The environmental effect, embodied energy, and CO\u003csub\u003e2\u003c/sub\u003e emissions are reduced when SF, SSA, and RP are added to the concrete as an aggregate and binder.\u003c/p\u003e","manuscriptTitle":"Valorization of Industrial Byproducts in Concrete: Synergistic Effects of Sewage Sludge Ash and Silica Fume with Recycled Plastic Fine Aggregates","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-19 15:29:20","doi":"10.21203/rs.3.rs-7207003/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-09-10T17:54:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-01T13:55:11+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-23T18:21:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-14T05:47:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"13198803799734304497509304235743015059","date":"2025-08-11T16:28:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"320445381679934929085771014146266028999","date":"2025-08-11T14:23:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193484201982839354911195961513629301040","date":"2025-08-11T14:03:08+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-11T13:57:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-07T12:23:14+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-08-05T11:25:48+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-04T18:26:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Concrete and Cement","date":"2025-08-04T18:22:17+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":false,"email":"","identity":"discover-concrete-and-cement","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Discover Concrete and Cement","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"Unsupported Journal","inReviewEnabled":false,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d5acff2f-4c3d-4809-9424-d1e4ecee98d7","owner":[],"postedDate":"August 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-22T07:53:52+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-19 15:29:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7207003","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7207003","identity":"rs-7207003","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}