Evaluation of Mechanical Behavior of Treated Recycled Aggregate Concrete Modified with SCMs

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P. Ahirrao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7025923/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The increasing demand for sustainable construction materials has emphasized the need to incorporate recycled aggregates and supplementary cementitious materials (SCMs) into structural concrete. This study examines the mechanical behavior of M30 grade concrete incorporating 100% treated recycled coarse aggregates (TRCA), with and without SCMs including fly ash (FA), silica fume (SF), and nano-silica (NS). A total of five mixes were prepared as per IS 10262:2019: a control mix with natural aggregates and four mixes using TRCA, three of which incorporated individual SCMs. Experimental evaluations included compressive strength at 7, 14, 28, and 90 days, split tensile strength at 28 and 90 days, and static modulus of elasticity at 28 days in accordance with IS 516:2013. Results indicated that concrete with TRCA alone showed slightly lower mechanical properties compared to the control mix. However, the inclusion of SCMs significantly enhanced performance. Notably, the mix containing 2% nano-silica achieved the highest values for compressive strength (52.4 MPa at 90 days), split tensile strength (4.6 MPa at 90 days), and elastic modulus (31,400 MPa), outperforming the control. The improvements are attributed to the pozzolanic activity and particle refinement effects of NS, which enhanced matrix densification and interfacial bonding. The findings demonstrate that the combined use of TRCA and nano-silica offers a sustainable and high-performance alternative to conventional concrete, aligning with circular economy principles and advancing the development of eco-efficient construction materials Recycled Aggregate Concrete (RAC) Treated Recycled Concrete Aggregate (TRCA) Supplementary Cementitious Materials (SCMs) Sustainable Construction Mechanical Properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction In the construction industry, the emphasis on sustainable alternatives has increased due to the growing urgency to reduce resource depletion and environmental degradation. Due to the high demand for cement and the extraction of virgin aggregates, concrete—the most widely used building material globally—puts a tremendous strain on natural resources. In an effort to reduce environmental impact and advance circular economy principles, this has sparked the development of Recycled Aggregate Concrete (RAC), which integrates Recycled Concrete Aggregates (RCA) made from construction and demolition waste. [ 1 ] ; [ 2 ] However, the main drawback of RAC is that untreated RCA is of lower quality and usually has adhered mortar, low density, and high water absorption. The durability and mechanical qualities of RAC are negatively impacted by these traits [ 3 ];[ 4 ]. Recent developments have responded by emphasizing the use of treatment methods to improve the quality of RCA. Interestingly, mechanical abrasion after acid soaking has been successful in strengthening aggregates and eliminating weak mortar. [ 5 ] At the same time, adding supplementary cementitious materials (SCMs) like fly ash, silica fume, and nano-silica has become a potent way to improve RAC performance. These substances support matrix densification, pozzolanic reactions, and refined microstructures, which enhance compressive strength and durability over time[ 6 ]. The interfacial transition zone (ITZ) and hydration behavior in treated RAC can now be better understood by experts through the combination of sophisticated characterization methods like Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD). Furthermore, RAC's case as a sustainable material is strengthened by the growing use of cutting-edge digital tools like Life Cycle Assessment (LCA) and Building Information Modelling (BIM) to assess its economic and environmental performance[ 7 ]. The combination of analytical tools, SCMs, and treatment techniques points to a promising future for RAC in terms of meeting sustainability and performance standards. The mechanical, microstructural, and durability performance of M30 grade RAC is examined in this study in relation to dual-stage treated RCA and SCMs. The results are intended to give a comprehensive grasp of the developments that are turning RAC into an environmentally friendly and technically sound concrete for contemporary infrastructure. 2 Materials and Methods 2.1 Materials 2.1.1 Cement and Supplementary Cementitious Materials (SCMs) Ordinary Portland Cement (OPC) conforming to IS 12269:2013[ 8 ] was used throughout the study. To enhance durability and matrix densification, three SCMs were incorporated: Class F Fly Ash[ 9 ] (IS 3812-1:2013), Silica Fume[ 10 ] (IS 15388:2003), and Nano-Silica (average particle size ~ 30 nm). These were selected for their proven pozzolanic activity and ability to improve microstructure and long-term performance. 2.1.2 Aggregates Natural coarse aggregates (NCA) of 20 mm nominal size and natural river sand conforming to[ 11 ] were used for control concrete. Recycled concrete aggregates (RCA) were sourced from demolished M25–M30 grade concrete. The RCA was screened and processed to ensure particle sizes between 4.75 mm and 20 mm. 2.1.3 RCA Treatment Process As shown in Fig. 1 , the presence of adhered mortar on the surface of recycled aggregates significantly influences their physical properties, including increased porosity and water absorption. This necessitates treatment processes to improve aggregate quality and enhance the performance of RAC [ 11 ]. The RCA underwent a two-stage treatment to improve physical and mechanical characteristics: Acid Soaking: RCA was immersed in 5% hydrochloric acid (HCl) solution for 24 hours to dissolve adhered mortar and increase surface roughness. It was subsequently rinsed and dried[ 1 ] Mechanical Abrasion: The dried RCA was subjected to 10 minutes of dry abrasion in a Los Angeles machine (without steel balls) to dislodge weakened particles. This dual treatment significantly improved water absorption, crushing value, and surface integrity . 2.1.4 Water and Super plasticizer Potable tap water conforming to [ 12 ] was used for mixing and curing. A polycarboxylate-based high-range water-reducing admixture was added to enhance workability, especially in mixes incorporating nano-silica. 2.2 Mix Proportions Concrete mixes were designed for M30 grade as per[ 13 ]. A total of five mixes were prepared: NAC – Control concrete with NCA only; RAC + TRCA – RAC with 100% treated RCA; RAC + TRCA + 15% FA – RAC with 15% Fly Ash as cement replacement; RAC + TRCA + 10% SF – RAC with 10% Silica Fume; RAC + TRCA + 2% NS – RAC with 2% Nano-Silica by weight of cement The water–binder ratio was kept at 0.42 for all mixes. Mix proportions were adjusted based on aggregate moisture and absorption characteristics. 2.3 Testing and Characterization To evaluate the mechanical performance of the prepared concrete mixes, a series of standardized tests were conducted in accordance with relevant Indian Standards. The tests included compressive strength, split tensile strength, and static modulus of elasticity. All specimens were cast in steel moulds, demoulded after 24 hours, and cured in potable water at 27 ± 2°C until the time of testing. 2.3.1 Compressive Strength Compressive strength tests were performed on standard 150 mm cube specimens at curing intervals of 7, 14, 28, and 90 days as per the procedures outlined in[ 14 ]. A calibrated compression testing machine (CTM) with a capacity of 2000 kN was used, applying a uniform load at a rate of 0.5 MPa/sec until failure. The average value of three specimens was reported for each mix and age. 2.3.2 Split Tensile Strength Split tensile strength tests were carried out on 150 mm diameter × 300 mm height cylindrical specimens in accordance with[ 15 ] at 28 and 90 days of curing. The test involved applying a diametral compressive load until failure, and the average of three specimens was recorded for each mix and age group. 2.3.3 Static Modulus of Elasticity The static modulus of elasticity was determined as per [ 14 ] IS 516 : 1959 using cylindrical specimens of size 150 mm × 300 mm, tested at 28 days. A compress meter was mounted on the specimen to measure longitudinal strain under axial loading. The modulus was computed as the slope of the stress–strain curve within the specified loading range. All mechanical tests were performed under controlled laboratory conditions. The results were used to evaluate the effectiveness of treated RCA and the influence of supplementary cementitious materials on the structural performance of recycled aggregate concrete. 3 Results and Discussion This section presents a comparative analysis of the mechanical, microstructural, and durability performance of normal aggregate concrete (NAC) and recycled aggregate concrete (RAC) incorporating treated RCA and supplementary cementitious materials (SCMs). 3.1 Aggregate Quality Enhancement Recycled concrete aggregates (RCA) inherently exhibit inferior quality compared to natural aggregates due to the presence of adhered mortar, micro cracks, and higher porosity. These characteristics result in lower specific gravity, higher water absorption, and reduced mechanical performance, which can compromise the durability and strength of concrete made with untreated RCA. Therefore, enhancing the quality of RCA through appropriate treatment methods is critical for its effective use in structural-grade concrete such as M30. In this study, the RCA was treated using a two-step process involving acid soaking followed by mechanical abrasion. The primary objectives of this treatment were to: Remove loosely adhered mortar, Reduce the total porosity and surface roughness, Improve particle strength and density. Tests conducted as per IS 2386 (Part 1 to 4): 1963 revealed notable improvements in the physical properties of treated RCA (TRCA) over untreated RCA (URCA): Table 1 physical properties of treated RCA (TRCA) over untreated RCA (URCA) Property IS Code URCA TRCA Improvement (%) Specific Gravity IS 2386 (Part 3) 2.41 2.55 ↑ 5.81% Water Absorption (%) IS 2386 (Part 3) 4.5 2.3 ↓ 48.9% Crushing Value (%) IS 2386 (Part 4) 27.8 21.4 ↓ 23.0% Impact Value (%) IS 2386 (Part 4) 25.5 18.9 ↓ 25.9% Abrasion Value (%) IS 2386 (Part 4) 33.2 26.5 ↓ 20.2% The reduction in water absorption and improvement in mechanical indices signify a more compact and durable aggregate skeleton suitable for higher-grade concrete. The acid soaking dissolved a portion of the residual cement paste, while the mechanical abrasion smoothed surface textures and removed weak zones. 3.2 Mechanical Properties 3.2.1 Compressive Strength The control mix (NAC) achieved a 28-day compressive strength of 39.5 MPa, meeting the target strength for M30 concrete. The RAC + TRCA mix showed a slight reduction in strength across all curing ages compared to NAC, attributed to the weaker nature of recycled aggregates despite being treated. The addition of 15% Fly Ash improved long-term strength, with 47.1 MPa at 90 days, due to the pozzolanic reaction that becomes more effective over time. 10% Silica Fume enhanced early and long-term strength, yielding 40.3 MPa at 28 days and 49.5 MPa at 90 days, indicating densification of the microstructure. 2% Nano-Silica resulted in the highest strength among all mixes, with 42 MPa at 28 days and 52.4 MPa at 90 days, demonstrating the significant pozzolanic and filler effects of nano-silica in improving the interfacial transition zone (ITZ) and matrix densification. Table 2 Compressive Strength (MPa) Mix Type 7 Days 14 Days 28 Days 90 Days NAC (Control) 26.2 33.7 39.5 45.6 RAC + TRCA 24 31 37.2 44 RAC + TRCA + 15% Fly Ash 23.1 30.5 38.5 47.1 RAC + TRCA + 10% Silica Fume 25 33 40.3 49.5 RAC + TRCA + 2% Nano-Silica 26 34.5 42 52.4 3.2.2 Split Tensile Strength and Modulus of Elasticity Tensile strength increased moderately in TRCA mixes, particularly with nano-silica and silica fume. Modulus of elasticity showed improved stiffness for TRCA mixes, with up to 10% enhancement observed in the nano-silica series. The presence of SCMs played a key role in refining pore structure and enhancing load transfer capabilities (Li et al., 2019). Table 3 Split Tensile Strength (MPa) (at 28 and 90 Days) Mix Type 28 Days 90 Days NAC (Control) 3.6 4.1 RAC + TRCA 3.3 3.9 RAC + TRCA + 15% Fly Ash 3.5 4.2 RAC + TRCA + 10% Silica Fume 3.7 4.4 RAC + TRCA + 2% Nano-Silica 3.9 4.6 The control mix (NAC) recorded tensile strengths of 3.6 MPa at 28 days and 4.1 MPa at 90 days, serving as the benchmark. RAC + TRCA showed a minor reduction in strength (~ 8% lower than NAC at 28 days), due to the inherent weakness of RCA and potential microcracks despite treatment. Incorporation of 15% fly ash slightly improved tensile strength, with 4.2 MPa at 90 days, likely due to better paste-aggregate bonding over time via pozzolanic activity. Silica fume (10%) significantly enhanced tensile strength to 3.7 MPa at 28 days and 4.4 MPa at 90 days, attributed to improved ITZ and refined pore structure. The nano-silica mix (2%) achieved the highest tensile strength across all mixes, with 3.9 MPa at 28 days and 4.6 MPa at 90 days, confirming its superior filler and nucleation effects leading to a denser matrix and stronger bond within the composite. The control mix (NAC) exhibited a static modulus of 30,500 MPa, which aligns with expected values for M30 grade concrete. The use of 100% TRCA in RAC led to a reduction (~ 7.5%) in modulus compared to NAC, due to the lower stiffness and higher porosity of recycled aggregates. Fly ash (15%) marginally improved the modulus to 29,000 MPa, likely because of better packing density and gradual pozzolanic gain. Silica fume (10%) enhanced the modulus almost to control levels (30,100 MPa), demonstrating its effectiveness in refining the microstructure and improving elastic behavior. The nano-silica-modified mix (2%) achieved the highest modulus (31,400 MPa) — even surpassing NAC — which can be attributed to its high reactivity and ability to densify the ITZ, improving both stiffness and load transfer efficiency. Table 4 Modulus of Elasticity (MPa) (at 28 Days, as per IS 516:2013) Mix Type Static Elastic Modulus NAC (Control) 30,500 RAC + TRCA 28,200 RAC + TRCA + 15% Fly Ash 29,000 RAC + TRCA + 10% Silica Fume 30,100 RAC + TRCA + 2% Nano-Silica 31,400 4 Conclusion This study investigated the mechanical performance of M30 grade concrete incorporating 100% treated recycled coarse aggregates (TRCA), with and without supplementary cementitious materials (SCMs) such as fly ash, silica fume, and nano-silica. The results led to the following key conclusions: The control mix (NAC) achieved a 28-day strength of 39.5 MPa, while RAC with TRCA alone showed a slight reduction (37.2 MPa). However, the inclusion of SCMs significantly improved strength, with the highest gain observed in the nano-silica mix (42.0 MPa at 28 days and 52.4 MPa at 90 days), surpassing even the control. Similar trends were observed in split tensile strength. RAC + TRCA + 2% nano-silica attained the highest tensile strength of 3.9 MPa (28 days) and 4.6 MPa (90 days), indicating improved matrix cohesion and interfacial bonding. The use of TRCA alone reduced the elastic modulus (28,200 MPa) compared to NAC (30,500 MPa). However, silica fume and nano-silica mixes effectively restored and enhanced this property, with the nano-silica mix achieving the highest modulus of 31,400 MPa. Among the SCMs studied, nano-silica proved to be the most effective in enhancing mechanical properties, followed by silica fume and fly ash. The pozzolanic reactivity and particle fineness of nano-silica contributed to a denser microstructure and improved interfacial transition zone (ITZ). The use of treated recycled aggregates along with SCMs like nano-silica offers a viable and sustainable alternative to natural aggregates, improving both performance and environmental impact. This aligns with circular economy principles and promotes eco-efficient construction. Declarations I so certify that the study project I did, Pravin Ankushrao Nikam with the title “Evaluation of Mechanical Behavior of Treated Recycled Aggregate Concrete Modified with SCMs” is an original work of mine. No other university or magazine has previously accepted this work, in whole or in part, for the granting of a degree, diploma, or publication. Additionally, I affirm that all of the data and material included in this work was gathered and handled with academic integrity, and that all references were properly cited. I am the only one accountable for the work's substance; any mistakes or omissions are accidental and my fault. The corresponding author can provide the datasets created and/or analyzed during the current study upon reasonable request. Corresponding author Pravin Ankushrao Nikam E mail: [email protected] Orcid id : https://orcid.org/0000-0003-3115-7564 Linkedin: https://www.linkedin.com/in/pravin-nikam-42b784103 Facebook: https://www.facebook.com/pravinnikam87 Tweeter: @pravinnikam87 Funding Source: - There is no funding or financial support for this research work Clinical Trial: Not applicable for this paper There is no conflict between authors Ethics, Consent to Participate, and Consent to Publish declarations: not applicable. References Vivian W.Y. Tam, X.F. Gao, C.M. Tam, Microstructural analysis of recycled aggregate concrete produced from two-stage mixing approach, 35 (2005) 1195–1203. https://doi.org/10.1016/j.cemconres.2004.10.025. R. V Silva, J. De Brito, R.K. Dhir, Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production, Constr. Build. Mater. 65 (2014) 201–217. https://doi.org/10.1016/j.conbuildmat.2014.04.117. C.S. Poon, Z.H. Shui, L. Lam, Effect of microstructure of ITZ on compressive strength of concrete prepared with recycled aggregates, 18 (2004) 461–468. https://doi.org/10.1016/j.conbuildmat.2004.03.005. Chi-Sun Poon, Dixon Chan, The use of recycled aggregate in concrete in Hong Kong, Resour. Conserv. Recycl. 50 (2007) 293–305. https://doi.org/10.1016/j.resconrec.2006.06.005. S.C. Kou, C.S. Poon, Enhancing the durability properties of concrete prepared with coarse recycled aggregate, Constr. Build. Mater. 35 (2012) 69–76. https://doi.org/10.1016/j.conbuildmat.2012.02.032. Daman K. Panesar., Supplementary cementing materials, Elsevier LTD, 2019. https://doi.org/10.1016/B978-0-08-102616-8.00003-4. G. Habert, S. A. Miller, V. M. John, J. L. Provis, A. Favier, A. Horvath, K. L. Scrivener, Environmental impacts and decarbonization strategies in the cement and concrete industries, Nat. Rev. Earth Environ. (n.d.). https://doi.org/10.1038/s43017-020-0093-3. IS12269, Ordinary Portland cement, 53 grade — specification, Bur. Indian Stand. New Delhi. (2013). IS 3812 (Part 1):2013, Pulverized Fuel Ash — Specification, Bur. Indian Stand. New Delhi. (2013) 1–11. IS 15388:2003, Silica fume — specification, Bur. Indian Stand. New Delhi. 1–7 (2003). IS383:, Coarse and Fine Aggregate For Concrete -Specification, Bur. Indian Stand. New Delhi. (2016) 1–19. IS 456, Plain Concrete and Reinforced, Bur. Indian Stand. Dehli. (2000) 1–114. IS 10262, Concrete Mix Proportioning - Guidelines, Bur. Indian Stand. New Delhi. (2009) 1–14. IS 516:1959, Method of Tests for Strength of Concrete, Bur. Indian Stand. (1959). IS 5816, Indian standard Splitting tensile strength of concrete- method of test, Bur. Indian Stand. (1999) 1–14. Table 5 To 8 Table 5 To 8 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files AnexureI.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7025923","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":530182183,"identity":"db0b7171-7f9d-4d6f-a759-ac3f80817b31","order_by":0,"name":"Pravin Ankushrao Nikam","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYLCCBCBm4wESHxgYGBuggjxEaWGcQbQWmBJmHiQtOIG59OFnEg93MOTx8Rx+utnmzx3Z/vbmAww/ahhkzHFosexLM5NIPMNQzMbbZnY7t+2Z8YwzxxIYe44x8FjisM/gDIOxQWIbQ2IbPwNQS8PhxA0SOQYMvA0MPAYHcGlh/wzVwv7ttsUfkJb8D4x/8WrhMXwA1sLbY3abgQ1sCwMzPlsse3gKgVokEtt4zpTd7G07DPKLwWGZYxI4tZjzsG84+LPNJnF+T/q2Gz/+HAaF2MOHb2ps7HE6DEJJoIoewBDB1DIKRsEoGAWjAA8AAPjdWqVFLo0YAAAAAElFTkSuQmCC","orcid":"","institution":"SND College of Engineering \u0026 Research Centre","correspondingAuthor":true,"prefix":"","firstName":"Pravin","middleName":"Ankushrao","lastName":"Nikam","suffix":""},{"id":530182187,"identity":"1f25a008-92fd-43a7-b773-54fcb2164562","order_by":1,"name":"Arun Kumar Dwivedi","email":"","orcid":"","institution":"Sandip University","correspondingAuthor":false,"prefix":"","firstName":"Arun","middleName":"Kumar","lastName":"Dwivedi","suffix":""},{"id":530182189,"identity":"4574af5b-c4fd-4846-bfb2-3ff37b8c40c3","order_by":2,"name":"S. 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14:58:31","extension":"xml","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":70100,"visible":true,"origin":"","legend":"","description":"","filename":"ff08144fabb64121ba91e455b773713b1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/b15ddaad9c61a23795a06484.xml"},{"id":93699558,"identity":"8737a3d0-66f9-4846-8067-a919646ca7ac","added_by":"auto","created_at":"2025-10-16 15:22:31","extension":"html","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":82483,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/bd8fbf3acda6058ddd97dabb.html"},{"id":93697546,"identity":"3761967d-4a8e-433f-adff-793c53670e51","added_by":"auto","created_at":"2025-10-16 14:58:31","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":81568,"visible":true,"origin":"","legend":"\u003cp\u003eVisual representation of adhered mortar on recycled coarse aggregate particles. The left image (processed effect) and the right image (actual samples) both show mortar remnants (highlighted by arrows), which affect the density, porosity, and bonding quality of RCA in concrete mixes.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/70c7100a6fce5803396eb9bb.png"},{"id":93696125,"identity":"dfb987d3-1bfd-4585-93a7-507e7e7c23f0","added_by":"auto","created_at":"2025-10-16 14:50:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":65471,"visible":true,"origin":"","legend":"\u003cp\u003eComparison between untreated and treated recycled coarse aggregate (RCA). The untreated RCA (left) exhibits a significant amount of adhered mortar, which can negatively impact concrete performance by increasing porosity and reducing strength. In contrast, the treated RCA (right) shows a visibly cleaner surface with minimal mortar residues, indicating improved quality suitable for use in recycled aggregate concrete (RAC).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/bfbf84541281e5d8a4367dae.png"},{"id":93696124,"identity":"92ddfe07-f9fa-4526-b57b-cd68ef2d0c06","added_by":"auto","created_at":"2025-10-16 14:50:31","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":42089,"visible":true,"origin":"","legend":"\u003cp\u003eobjectives of treatment\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/34bc156340c0ec30c85bd0a8.png"},{"id":93696128,"identity":"68bf8e20-dc54-4278-b400-8609b871debf","added_by":"auto","created_at":"2025-10-16 14:50:31","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":53116,"visible":true,"origin":"","legend":"\u003cp\u003ePhysical properties of treated RCA (TRCA) over untreated RCA (URCA)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/1c6edf78bfe29863f7c48202.png"},{"id":93696133,"identity":"01a942ff-1584-449b-9669-ca6a276b6f31","added_by":"auto","created_at":"2025-10-16 14:50:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":77922,"visible":true,"origin":"","legend":"\u003cp\u003eCompressive Strength of Concrete Mixes Over Time.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/0dc08359c9e07ed21fda52ce.png"},{"id":93696129,"identity":"b592fee3-db9e-44d9-809d-567e1b1d4251","added_by":"auto","created_at":"2025-10-16 14:50:31","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":79709,"visible":true,"origin":"","legend":"\u003cp\u003eTensile Strength of Concrete Mixes at 28 and 90 Days\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/7c02491bd3240a8e0acbf733.png"},{"id":93698136,"identity":"fbdce91d-1b62-4d09-b993-5a5c399b3bfe","added_by":"auto","created_at":"2025-10-16 15:06:31","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":49240,"visible":true,"origin":"","legend":"\u003cp\u003eModulus of Elasticity of Concrete Mixes at 28 Days\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/9bbef34ccde1c53965ddb8db.png"},{"id":95523637,"identity":"8290b2ce-d81f-4453-9429-690136396538","added_by":"auto","created_at":"2025-11-10 09:59:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1190678,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/16b44493-2ba5-4add-8edb-9e97e8009a86.pdf"},{"id":93697550,"identity":"e7b9763c-6add-4b5e-8699-f0e6fa985fb6","added_by":"auto","created_at":"2025-10-16 14:58:31","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":458396,"visible":true,"origin":"","legend":"","description":"","filename":"AnexureI.docx","url":"https://assets-eu.researchsquare.com/files/rs-7025923/v1/3789aec34f83ed4003143278.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of Mechanical Behavior of Treated Recycled Aggregate Concrete Modified with SCMs","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eIn the construction industry, the emphasis on sustainable alternatives has increased due to the growing urgency to reduce resource depletion and environmental degradation. Due to the high demand for cement and the extraction of virgin aggregates, concrete\u0026mdash;the most widely used building material globally\u0026mdash;puts a tremendous strain on natural resources. In an effort to reduce environmental impact and advance circular economy principles, this has sparked the development of Recycled Aggregate Concrete (RAC), which integrates Recycled Concrete Aggregates (RCA) made from construction and demolition waste. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003csup\u003e;\u003c/sup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eHowever, the main drawback of RAC is that untreated RCA is of lower quality and usually has adhered mortar, low density, and high water absorption. The durability and mechanical qualities of RAC are negatively impacted by these traits [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e];[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Recent developments have responded by emphasizing the use of treatment methods to improve the quality of RCA. Interestingly, mechanical abrasion after acid soaking has been successful in strengthening aggregates and eliminating weak mortar. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eAt the same time, adding supplementary cementitious materials (SCMs) like fly ash, silica fume, and nano-silica has become a potent way to improve RAC performance. These substances support matrix densification, pozzolanic reactions, and refined microstructures, which enhance compressive strength and durability over time[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. The interfacial transition zone (ITZ) and hydration behavior in treated RAC can now be better understood by experts through the combination of sophisticated characterization methods like Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD).\u003c/p\u003e\u003cp\u003eFurthermore, RAC's case as a sustainable material is strengthened by the growing use of cutting-edge digital tools like Life Cycle Assessment (LCA) and Building Information Modelling (BIM) to assess its economic and environmental performance[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The combination of analytical tools, SCMs, and treatment techniques points to a promising future for RAC in terms of meeting sustainability and performance standards.\u003c/p\u003e\u003cp\u003eThe mechanical, microstructural, and durability performance of M30 grade RAC is examined in this study in relation to dual-stage treated RCA and SCMs. The results are intended to give a comprehensive grasp of the developments that are turning RAC into an environmentally friendly and technically sound concrete for contemporary infrastructure.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Materials\u003c/h2\u003e\u003cdiv id=\"Sec4\" class=\"Section3\"\u003e\u003ch2\u003e2.1.1 Cement and Supplementary Cementitious Materials (SCMs)\u003c/h2\u003e\u003cp\u003eOrdinary Portland Cement (OPC) conforming to IS 12269:2013[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] was used throughout the study. To enhance durability and matrix densification, three SCMs were incorporated: Class F Fly Ash[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] (IS 3812-1:2013), Silica Fume[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] (IS 15388:2003), and Nano-Silica (average particle size\u0026thinsp;~\u0026thinsp;30 nm). These were selected for their proven pozzolanic activity and ability to improve microstructure and long-term performance.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.1.2 Aggregates\u003c/h2\u003e\u003cp\u003eNatural coarse aggregates (NCA) of 20 mm nominal size and natural river sand conforming to[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] were used for control concrete. Recycled concrete aggregates (RCA) were sourced from demolished M25\u0026ndash;M30 grade concrete. The RCA was screened and processed to ensure particle sizes between 4.75 mm and 20 mm.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.1.3 RCA Treatment Process\u003c/h2\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the presence of adhered mortar on the surface of recycled aggregates significantly influences their physical properties, including increased porosity and water absorption. This necessitates treatment processes to improve aggregate quality and enhance the performance of RAC [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe RCA underwent a two-stage treatment to improve physical and mechanical characteristics:\u003c/p\u003e\u003cp\u003eAcid Soaking: RCA was immersed in 5% hydrochloric acid (HCl) solution for 24 hours to dissolve adhered mortar and increase surface roughness. It was subsequently rinsed and dried[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eMechanical Abrasion: The dried RCA was subjected to 10 minutes of dry abrasion in a Los Angeles machine (without steel balls) to dislodge weakened particles. This dual treatment significantly improved water absorption, crushing value, and surface integrity .\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\u003ch2\u003e2.1.4 Water and Super plasticizer\u003c/h2\u003e\u003cp\u003ePotable tap water conforming to [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] was used for mixing and curing. A polycarboxylate-based high-range water-reducing admixture was added to enhance workability, especially in mixes incorporating nano-silica.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Mix Proportions\u003c/h2\u003e\u003cp\u003eConcrete mixes were designed for M30 grade as per[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. A total of five mixes were prepared:\u003c/p\u003e\u003cp\u003eNAC \u0026ndash; Control concrete with NCA only; RAC\u0026thinsp;+\u0026thinsp;TRCA \u0026ndash; RAC with 100% treated RCA;\u003c/p\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;15% FA \u0026ndash; RAC with 15% Fly Ash as cement replacement; RAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;10% SF \u0026ndash; RAC with 10% Silica Fume; RAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;2% NS \u0026ndash; RAC with 2% Nano-Silica by weight of cement\u003c/p\u003e\u003cp\u003eThe water\u0026ndash;binder ratio was kept at 0.42 for all mixes. Mix proportions were adjusted based on aggregate moisture and absorption characteristics.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Testing and Characterization\u003c/h2\u003e\u003cp\u003eTo evaluate the mechanical performance of the prepared concrete mixes, a series of standardized tests were conducted in accordance with relevant Indian Standards. The tests included compressive strength, split tensile strength, and static modulus of elasticity. All specimens were cast in steel moulds, demoulded after 24 hours, and cured in potable water at 27\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C until the time of testing.\u003c/p\u003e\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\u003ch2\u003e2.3.1 Compressive Strength\u003c/h2\u003e\u003cp\u003eCompressive strength tests were performed on standard 150 mm cube specimens at curing intervals of 7, 14, 28, and 90 days as per the procedures outlined in[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. A calibrated compression testing machine (CTM) with a capacity of 2000 kN was used, applying a uniform load at a rate of 0.5 MPa/sec until failure. The average value of three specimens was reported for each mix and age.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\u003ch2\u003e2.3.2 Split Tensile Strength\u003c/h2\u003e\u003cp\u003eSplit tensile strength tests were carried out on 150 mm diameter \u0026times; 300 mm height cylindrical specimens in accordance with[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] at 28 and 90 days of curing. The test involved applying a diametral compressive load until failure, and the average of three specimens was recorded for each mix and age group.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\u003ch2\u003e2.3.3 Static Modulus of Elasticity\u003c/h2\u003e\u003cp\u003eThe static modulus of elasticity was determined as per [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] IS 516 : 1959 using cylindrical specimens of size 150 mm \u0026times; 300 mm, tested at 28 days. A compress meter was mounted on the specimen to measure longitudinal strain under axial loading. The modulus was computed as the slope of the stress\u0026ndash;strain curve within the specified loading range.\u003c/p\u003e\u003cp\u003eAll mechanical tests were performed under controlled laboratory conditions. The results were used to evaluate the effectiveness of treated RCA and the influence of supplementary cementitious materials on the structural performance of recycled aggregate concrete.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cp\u003eThis section presents a comparative analysis of the mechanical, microstructural, and durability performance of normal aggregate concrete (NAC) and recycled aggregate concrete (RAC) incorporating treated RCA and supplementary cementitious materials (SCMs).\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Aggregate Quality Enhancement\u003c/h2\u003e\u003cp\u003eRecycled concrete aggregates (RCA) inherently exhibit inferior quality compared to natural aggregates due to the presence of adhered mortar, micro cracks, and higher porosity. These characteristics result in lower specific gravity, higher water absorption, and reduced mechanical performance, which can compromise the durability and strength of concrete made with untreated RCA. Therefore, enhancing the quality of RCA through appropriate treatment methods is critical for its effective use in structural-grade concrete such as M30.\u003c/p\u003e\u003cp\u003eIn this study, the RCA was treated using a two-step process involving acid soaking followed by mechanical abrasion. The primary objectives of this treatment were to: Remove loosely adhered mortar, Reduce the total porosity and surface roughness, Improve particle strength and density.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTests conducted as per IS 2386 (Part 1 to 4): 1963 revealed notable improvements in the physical properties of treated RCA (TRCA) over untreated RCA (URCA):\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ephysical properties of treated RCA (TRCA) over untreated RCA (URCA)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProperty\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIS Code\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eURCA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eTRCA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImprovement (%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\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\u003eIS 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026uarr; 5.81%\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\u003eIS 2386 (Part 3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026darr; 48.9%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCrushing Value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIS 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e27.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e21.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026darr; 23.0%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eImpact Value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIS 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e25.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e18.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026darr; 25.9%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbrasion Value (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eIS 2386 (Part 4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e33.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e26.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026darr; 20.2%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe reduction in water absorption and improvement in mechanical indices signify a more compact and durable aggregate skeleton suitable for higher-grade concrete. The acid soaking dissolved a portion of the residual cement paste, while the mechanical abrasion smoothed surface textures and removed weak zones.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Mechanical Properties\u003c/h2\u003e\u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\u003ch2\u003e3.2.1 Compressive Strength\u003c/h2\u003e\u003cp\u003eThe control mix (NAC) achieved a 28-day compressive strength of 39.5 MPa, meeting the target strength for M30 concrete. The RAC\u0026thinsp;+\u0026thinsp;TRCA mix showed a slight reduction in strength across all curing ages compared to NAC, attributed to the weaker nature of recycled aggregates despite being treated. The addition of 15% Fly Ash improved long-term strength, with 47.1 MPa at 90 days, due to the pozzolanic reaction that becomes more effective over time. 10% Silica Fume enhanced early and long-term strength, yielding 40.3 MPa at 28 days and 49.5 MPa at 90 days, indicating densification of the microstructure. 2% Nano-Silica resulted in the highest strength among all mixes, with 42 MPa at 28 days and 52.4 MPa at 90 days, demonstrating the significant pozzolanic and filler effects of nano-silica in improving the interfacial transition zone (ITZ) and matrix densification.\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\u003eCompressive Strength (MPa)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7 Days\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14 Days\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e28 Days\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e90 Days\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNAC (Control)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e39.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e45.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e37.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e44\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;15% Fly Ash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e38.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e47.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;10% Silica Fume\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e40.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e49.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;2% Nano-Silica\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e52.4\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=\"Sec17\" class=\"Section3\"\u003e\u003ch2\u003e3.2.2 Split Tensile Strength and Modulus of Elasticity\u003c/h2\u003e\u003cp\u003eTensile strength increased moderately in TRCA mixes, particularly with nano-silica and silica fume. Modulus of elasticity showed improved stiffness for TRCA mixes, with up to 10% enhancement observed in the nano-silica series. The presence of SCMs played a key role in refining pore structure and enhancing load transfer capabilities (Li et al., 2019).\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\u003eSplit Tensile Strength (MPa) (at 28 and 90 Days)\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMix Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e28 Days\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e90 Days\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNAC (Control)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;15% Fly Ash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;10% Silica Fume\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;2% Nano-Silica\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe control mix (NAC) recorded tensile strengths of 3.6 MPa at 28 days and 4.1 MPa at 90 days, serving as the benchmark. RAC\u0026thinsp;+\u0026thinsp;TRCA showed a minor reduction in strength (~\u0026thinsp;8% lower than NAC at 28 days), due to the inherent weakness of RCA and potential microcracks despite treatment. Incorporation of 15% fly ash slightly improved tensile strength, with 4.2 MPa at 90 days, likely due to better paste-aggregate bonding over time via pozzolanic activity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSilica fume (10%) significantly enhanced tensile strength to 3.7 MPa at 28 days and 4.4 MPa at 90 days, attributed to improved ITZ and refined pore structure. The nano-silica mix (2%) achieved the highest tensile strength across all mixes, with 3.9 MPa at 28 days and 4.6 MPa at 90 days, confirming its superior filler and nucleation effects leading to a denser matrix and stronger bond within the composite.\u003c/p\u003e\u003cp\u003eThe control mix (NAC) exhibited a static modulus of 30,500 MPa, which aligns with expected values for M30 grade concrete. The use of 100% TRCA in RAC led to a reduction (~\u0026thinsp;7.5%) in modulus compared to NAC, due to the lower stiffness and higher porosity of recycled aggregates. Fly ash (15%) marginally improved the modulus to 29,000 MPa, likely because of better packing density and gradual pozzolanic gain. Silica fume (10%) enhanced the modulus almost to control levels (30,100 MPa), demonstrating its effectiveness in refining the microstructure and improving elastic behavior. The nano-silica-modified mix (2%) achieved the highest modulus (31,400 MPa) \u0026mdash; even surpassing NAC \u0026mdash; which can be attributed to its high reactivity and ability to densify the ITZ, improving both stiffness and load transfer efficiency.\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\u003eModulus of Elasticity (MPa) (at 28 Days, as per IS 516:2013)\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\u003eMix Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStatic Elastic Modulus\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNAC (Control)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30,500\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e28,200\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;15% Fly Ash\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e29,000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;10% Silica Fume\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30,100\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;2% Nano-Silica\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e31,400\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eThis study investigated the mechanical performance of M30 grade concrete incorporating 100% treated recycled coarse aggregates (TRCA), with and without supplementary cementitious materials (SCMs) such as fly ash, silica fume, and nano-silica. The results led to the following key conclusions:\u003c/p\u003e\u003cp\u003eThe control mix (NAC) achieved a 28-day strength of 39.5 MPa, while RAC with TRCA alone showed a slight reduction (37.2 MPa). However, the inclusion of SCMs significantly improved strength, with the highest gain observed in the nano-silica mix (42.0 MPa at 28 days and 52.4 MPa at 90 days), surpassing even the control.\u003c/p\u003e\u003cp\u003eSimilar trends were observed in split tensile strength. RAC\u0026thinsp;+\u0026thinsp;TRCA\u0026thinsp;+\u0026thinsp;2% nano-silica attained the highest tensile strength of 3.9 MPa (28 days) and 4.6 MPa (90 days), indicating improved matrix cohesion and interfacial bonding.\u003c/p\u003e\u003cp\u003eThe use of TRCA alone reduced the elastic modulus (28,200 MPa) compared to NAC (30,500 MPa). However, silica fume and nano-silica mixes effectively restored and enhanced this property, with the nano-silica mix achieving the highest modulus of 31,400 MPa.\u003c/p\u003e\u003cp\u003eAmong the SCMs studied, nano-silica proved to be the most effective in enhancing mechanical properties, followed by silica fume and fly ash. The pozzolanic reactivity and particle fineness of nano-silica contributed to a denser microstructure and improved interfacial transition zone (ITZ).\u003c/p\u003e\u003cp\u003eThe use of treated recycled aggregates along with SCMs like nano-silica offers a viable and sustainable alternative to natural aggregates, improving both performance and environmental impact. This aligns with circular economy principles and promotes eco-efficient construction.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eI so certify that the study project I did, Pravin Ankushrao Nikam with the title \u0026ldquo;Evaluation of Mechanical Behavior of Treated Recycled Aggregate Concrete Modified with SCMs\u0026rdquo; is an original work of mine. No other university or magazine has previously accepted this work, in whole or in part, for the granting of a degree, diploma, or publication.\u003c/p\u003e\n\u003cp\u003eAdditionally, I affirm that all of the data and material included in this work was gathered and handled with academic integrity, and that all references were properly cited.\u003c/p\u003e\n\u003cp\u003eI am the only one accountable for the work\u0026apos;s substance; any mistakes or omissions are accidental and my fault.\u003c/p\u003e\n\u003cp\u003eThe corresponding author can provide the datasets created and/or analyzed during the current study upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorresponding author\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePravin Ankushrao Nikam\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eE mail: [email protected]\u003c/p\u003e\n\u003cp\u003eOrcid id\u003cstrong\u003e: \u003c/strong\u003ehttps://orcid.org/0000-0003-3115-7564\u003c/p\u003e\n\u003cp\u003eLinkedin: https://www.linkedin.com/in/pravin-nikam-42b784103\u003c/p\u003e\n\u003cp\u003eFacebook: https://www.facebook.com/pravinnikam87\u003c/p\u003e\n\u003cp\u003eTweeter: @pravinnikam87\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eFunding Source: - \u0026nbsp; There is no funding or financial support for this research work\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial: Not applicable\u0026nbsp;for this paper\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThere is no conflict between authors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics, Consent to Participate, and Consent to Publish declarations: not applicable.\u003c/strong\u003e\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eVivian W.Y. Tam, X.F. Gao, C.M. Tam, Microstructural analysis of recycled aggregate concrete produced from two-stage mixing approach, 35 (2005) 1195\u0026ndash;1203. https://doi.org/10.1016/j.cemconres.2004.10.025.\u003c/li\u003e\n\u003cli\u003eR. V Silva, J. De Brito, R.K. Dhir, Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production, Constr. Build. Mater. 65 (2014) 201\u0026ndash;217. https://doi.org/10.1016/j.conbuildmat.2014.04.117.\u003c/li\u003e\n\u003cli\u003eC.S. Poon, Z.H. Shui, L. Lam, Effect of microstructure of ITZ on compressive strength of concrete prepared with recycled aggregates, 18 (2004) 461\u0026ndash;468. https://doi.org/10.1016/j.conbuildmat.2004.03.005.\u003c/li\u003e\n\u003cli\u003eChi-Sun Poon, Dixon Chan, The use of recycled aggregate in concrete in Hong Kong, Resour. Conserv. Recycl. 50 (2007) 293\u0026ndash;305. https://doi.org/10.1016/j.resconrec.2006.06.005.\u003c/li\u003e\n\u003cli\u003eS.C. Kou, C.S. Poon, Enhancing the durability properties of concrete prepared with coarse recycled aggregate, Constr. Build. Mater. 35 (2012) 69\u0026ndash;76. https://doi.org/10.1016/j.conbuildmat.2012.02.032.\u003c/li\u003e\n\u003cli\u003eDaman K. Panesar., Supplementary cementing materials, Elsevier LTD, 2019. https://doi.org/10.1016/B978-0-08-102616-8.00003-4.\u003c/li\u003e\n\u003cli\u003eG. Habert, S. A. Miller, V. M. John, J. L. Provis, A. Favier, A. Horvath, K. L. Scrivener, Environmental impacts and decarbonization strategies in the cement and concrete industries, Nat. Rev. Earth Environ. (n.d.). https://doi.org/10.1038/s43017-020-0093-3.\u003c/li\u003e\n\u003cli\u003eIS12269, Ordinary Portland cement, 53 grade \u0026mdash; specification, Bur. Indian Stand. New Delhi. (2013).\u003c/li\u003e\n\u003cli\u003eIS 3812 (Part 1):2013, Pulverized Fuel Ash \u0026mdash; Specification, Bur. Indian Stand. New Delhi. (2013) 1\u0026ndash;11.\u003c/li\u003e\n\u003cli\u003eIS 15388:2003, Silica fume \u0026mdash; specification, Bur. Indian Stand. New Delhi. 1\u0026ndash;7 (2003).\u003c/li\u003e\n\u003cli\u003eIS383:, Coarse and Fine Aggregate For Concrete -Specification, Bur. Indian Stand. New Delhi. (2016) 1\u0026ndash;19.\u003c/li\u003e\n\u003cli\u003eIS 456, Plain Concrete and Reinforced, Bur. Indian Stand. Dehli. (2000) 1\u0026ndash;114.\u003c/li\u003e\n\u003cli\u003eIS 10262, Concrete Mix Proportioning - Guidelines, Bur. Indian Stand. New Delhi. (2009) 1\u0026ndash;14.\u003c/li\u003e\n\u003cli\u003eIS 516:1959, Method of Tests for Strength of Concrete, Bur. Indian Stand. (1959).\u003c/li\u003e\n\u003cli\u003eIS 5816, Indian standard Splitting tensile strength of concrete- method of test, Bur. Indian Stand. (1999) 1\u0026ndash;14.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table 5 To 8 ","content":"\u003cp\u003eTable 5 To 8 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Recycled Aggregate Concrete (RAC), Treated Recycled Concrete Aggregate (TRCA), Supplementary Cementitious Materials (SCMs), Sustainable Construction, Mechanical Properties","lastPublishedDoi":"10.21203/rs.3.rs-7025923/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7025923/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe increasing demand for sustainable construction materials has emphasized the need to incorporate recycled aggregates and supplementary cementitious materials (SCMs) into structural concrete. This study examines the mechanical behavior of M30 grade concrete incorporating 100% treated recycled coarse aggregates (TRCA), with and without SCMs including fly ash (FA), silica fume (SF), and nano-silica (NS). A total of five mixes were prepared as per IS 10262:2019: a control mix with natural aggregates and four mixes using TRCA, three of which incorporated individual SCMs. Experimental evaluations included compressive strength at 7, 14, 28, and 90 days, split tensile strength at 28 and 90 days, and static modulus of elasticity at 28 days in accordance with IS 516:2013.\u003c/p\u003e\n\u003cp\u003eResults indicated that concrete with TRCA alone showed slightly lower mechanical properties compared to the control mix. However, the inclusion of SCMs significantly enhanced performance. Notably, the mix containing 2% nano-silica achieved the highest values for compressive strength (52.4 MPa at 90 days), split tensile strength (4.6 MPa at 90 days), and elastic modulus (31,400 MPa), outperforming the control. The improvements are attributed to the pozzolanic activity and particle refinement effects of NS, which enhanced matrix densification and interfacial bonding.\u003c/p\u003e\n\u003cp\u003eThe findings demonstrate that the combined use of TRCA and nano-silica offers a sustainable and high-performance alternative to conventional concrete, aligning with circular economy principles and advancing the development of eco-efficient construction materials\u003c/p\u003e","manuscriptTitle":"Evaluation of Mechanical Behavior of Treated Recycled Aggregate Concrete Modified with SCMs","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-16 14:50:26","doi":"10.21203/rs.3.rs-7025923/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9ab4d03f-e2cd-44a5-a80b-d0fc67156cce","owner":[],"postedDate":"October 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-04T14:38:51+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-16 14:50:26","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7025923","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7025923","identity":"rs-7025923","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}