Study on rheological and mechanical properties optimization and mechanism of Nano-CaCO₃ regenerated aggregate concrete

Study on rheological and mechanical properties optimization and mechanism of Nano-CaCO₃ regenerated aggregate concrete | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Study on rheological and mechanical properties optimization and mechanism of Nano-CaCO₃ regenerated aggregate concrete Jun Xu, Guang-hua Lyu, Min Tan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8439637/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Apr, 2026 Read the published version in Scientific Reports → Version 1 posted 13 You are reading this latest preprint version Abstract To address poor rheological properties and low mechanical strength of recycled aggregate concrete (RAC) caused by recycled aggregate (RA) defects, this study investigated effects of nano-CaCO₃ (NC) on RAC's rheological (yield stress, plastic viscosity) and mechanical (compressive, splitting, flexural strength) properties under varying NC content (0%–2.5%), recycled aggregate replacement rates (0%–100%), and water-to-binder ratios (0.35–0.45). Orthogonal experiments optimized mix design, and SEM, XRD, MIP elucidated modification mechanisms. Results showed 1.0%–1.5% NC reduced yield stress by 23.6%–31.2% and plastic viscosity by 18.9%–25.3%, while increasing 28-day compressive strength by 20.3%–26.7%. Optimal mix (1.2% NC, 50% recycled aggregate replacement, 0.40 water-to-binder ratio) yielded RAC with construction-appropriate rheological properties and 28-day compressive strength of 52.8MPa (24.5% higher than reference). NC enhanced performance via pore refinement (filling effect), promoted hydration (nucleation effect), and improved aggregate-mortar interface (ITZ modification). This study provides theoretical and technical support for NC application in RAC engineering. Physical sciences/Engineering Physical sciences/Materials science nano CaCO₃ recycled aggregate concrete rheological properties mechanical properties interfacial transition zone optimization Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Research background and significance With the acceleration of urbanization and infrastructure upgrades in China, over 3 billion tons of construction solid waste are generated annually, with discarded concrete accounting for more than 40% of this total 1 . As a core product of recycled concrete resource utilization, recycled aggregate (RA) and its resulting recycled aggregate concrete (RAC) effectively reduce natural aggregate extraction and solid waste storage, aligning with the "dual carbon" goals and green building development concepts 2 , 3 . However, recycled aggregates, having undergone hydration hardening and fragmentation processes in original concrete, exhibit rough, porous surfaces with sharp edges and substantial hardened cement mortar layers. These characteristics result in RAC's poor rheological properties (low fluidity, tendency to segregate), insufficient mechanical strength, and inadequate durability, severely limiting its application in load-bearing structures 4 , 5 . Nanomaterials demonstrate significant potential in concrete modification due to their size effects, surface effects, and quantum effects 6 . Nano-Calcium Carbonate (NC), a low-cost and easily dispersible nanomodifier with particle sizes typically ranging from 20 to 100 nm, can refine concrete internal pores through the filling effect and accelerate cement hydration via the nucleation effect, thereby improving both microstructure and macroscopic properties 7 , 8 . While existing studies have shown NC's ability to enhance compressive strength and water resistance in ordinary concrete 9 , research on its synergistic optimization of rheological and mechanical properties in Regenerated Aggregate Concrete (RAC) remains limited. Particularly, there is a lack of comprehensive analysis of performance mechanisms under multi-factor interactions including NC dosage, recycled aggregate substitution rates, and water-to-binder ratios. Rheological properties directly determine RAC's workability and casting quality, while mechanical properties serve as the core indicator of structural load-bearing capacity. The synergistic optimization of these two aspects is crucial for achieving engineering applications of RAC 10 . Therefore, systematically investigating NC's influence on RAC's rheology and mechanical properties, optimizing mix proportions, and elucidating modification mechanisms holds significant theoretical and practical value for promoting efficient utilization of recycled aggregate resources and expanding RAC's application scenarios. State of research at home and abroad Performance defects and modification of regenerated aggregate concrete The "dual interface" characteristics of recycled aggregates (interface between recycled aggregates and adherent mortar, and between adherent mortar and fresh mortar) are the primary cause of RAC performance degradation. Li et al. found that when the recycled aggregate replacement rate increased from 0% to 100%, the 28-day compressive strength of RAC decreased by 15% to 30%, while the yield stress increased by over 40%, mainly due to the high water absorption rate of recycled aggregates causing increased viscosity of fresh concrete paste. To improve RAC performance, scholars have proposed physical modification methods (such as aggregate pretreatment and mechanical grinding) and chemical modification methods (such as adding mineral admixtures and chemical additives). Among these, Zhang Shuai et al. modified RAC using silica fume. When the silica fume dosage was 10%, the 28-day compressive strength increased by 18.2%, but the high specific surface area of silica fume tends to reduce concrete fluidity, requiring the use of high-efficiency water reducers. Research on the application of Nano-CaCO₃ in concrete The modified effects of NC in concrete are primarily manifested in three aspects: First, the filling effect, where NC particles fill capillary pores in cement paste and refine pore size distribution; Second, the nucleation effect, where active sites on NC surfaces adsorb cement hydration products to promote C-S-H gel formation; Third, the interface modification effect, where NC improves the structure of the interface transition zone between aggregates and cement paste, reducing interface cracks. Wang et al. demonstrated that when NC content reaches 1.0%, the 28-day compressive strength of ordinary concrete increases by 22.3% while porosity decreases by 14.5%. However, research on NC application in RAC still has limitations: On one hand, existing studies predominantly focus on mechanical properties while neglecting rheological performance, which is crucial for RAC construction quality; On the other hand, there is a lack of multi-factor interaction studies for performance optimization, making it challenging to directly guide engineering practices. Research gaps and the scope of this study Current research on NC-modified RAC reveals three key gaps: (1) The complex interplay between NC dosage, recycled aggregate substitution rate, and water-to-binder ratio on RAC's rheological and mechanical properties remains unclear; (2) Systematic investigation of NC's microstructural mechanisms for enhancing RAC's rheological performance is lacking; (3) Optimization methods that balance both rheological and mechanical properties are still absent. To address these issues, this study systematically investigates the effects of NC dosage, recycled aggregate substitution rate, and water-to-binder ratio on RAC's rheological properties (yield stress, plastic viscosity) and mechanical properties (compressive strength, tensile strength, flexural strength) through single-factor and orthogonal experiments. Using SEM, XRD, and MIP as microscopic characterization tools, we elucidate NC's modification mechanisms. The research ultimately proposes an optimal NC-modified RAC mix design that balances rheological and mechanical performance, providing a theoretical foundation for NC's engineering applications in RAC. Experimental materials and methods Test materials Gelation materials Ordinary Portland cement (OPC) with P·O 42.5 grade is adopted, whose performance indexes meet the requirements of "General Portland Cement" (GB 175–2007), and the main performance indexes are shown in Table 1 . Table 1 Main performance indicators of P·O 42.5 cement. Fineness (80µm sieve residue)/% initial setting time /min Settling time (min) 3D compressive strength/MPa 28d compressive strength/MPa 3D flexural strength/MPa 28d flexural strength/MPa 2.8 185 240 25.3 48.6 4.6 7.2 Nano CaCO₃ The industrial-grade nano CaCO₃ powder (30-80nm particle size, ≥ 99% purity, 35-45m²/g specific surface area) was prepared. Its XRD pattern (Fig. 1 ) shows predominantly calcite-type CaCO₃ with excellent crystallinity. To enhance dispersion, the powder was ultrasonically dispersed for 10 minutes using a 200W,40kHz ultrasonic disperser. Aggregates Natural Aggregate (NA): Coarse aggregate consists of limestone crushed stone with continuous 5-20mm gradation, featuring an apparent density of 2780 kg/m³, bulk density of 1650 kg/m³, and clay content of 0.3%. Fine aggregate is river sand with a fineness modulus of 2.6, apparent density of 2650 kg/m³, bulk density of 1580 kg/m³, and clay content of 1.2%, meeting the requirements of "Sand for Construction" (GB/T 14684 − 2022). Regenerated Aggregate (RA): Made from 20-year-old discarded reinforced concrete beams, this recycled coarse aggregate undergoes crushing and screening to produce continuous 5-20mm gradation. Its performance indicators are detailed in Table 2 . According to "Regenerated Coarse Aggregate for Concrete" (GB/T 25177 − 2010), this recycled aggregate is classified as Class II. Table 2 Main performance indicators of recycled coarse aggregates (Class II). Apparent density (kg/m³) Bulk density (kg/m³) water absorption /% sediment percentage /% Crush Indicator/% Adhesive mortar content/% 2450 1520 5.8 0.5 12.3 22.6 Additives and water The product employs a polycarboxylate-based high-efficiency water reducer with a solid content of 40% and a water reduction rate of ≥ 30%, meeting the requirements of 'Concrete Admixtures' (GB 8076 − 2008). The test water is tap water. Test protocol Design principles for mix proportions Using C40 concrete as the reference, the baseline mix design (0% NC admixture and 0% recycled aggregate replacement rate) consists of: cement 420 kg/m³, natural coarse aggregate 1180 kg/m³, river sand 650 kg/m³, water 168 kg/m³, and water reducer 1.2% (as a percentage of cementitious material mass). To mitigate the high water absorption characteristics of recycled aggregates, a 24-hour pre-wetting treatment was applied prior to use, maintaining a surface moisture content of 2%. The experimental variables included: NC admixture levels (0%,0.5%,1.0%,1.5%,2.0%,2.5% based on cementitious material mass), recycled aggregate replacement rates (0%,25%,50%,75%,100% based on total coarse aggregate mass), and water-cement ratio (0.35,0.40,0.45). Single factor test design The single-factor experiment was conducted to evaluate the impact of a single variable on RAC performance, with experimental groups as shown in Table 3 . Specifically, Groups 1–6 maintained a 50% recycled aggregate replacement rate and water-to-binder ratio of 0.40 while varying the NC content; Groups 7–11 kept the NC content at 1.0% and water-to-binder ratio at 0.40 while adjusting the recycled aggregate replacement rate; Groups 12–14 fixed the NC content at 1.0% and recycled aggregate replacement rate at 50%, while modifying the water-to-binder ratio. Table 3 Single-factor experimental design scheme and grouping parameters. Trial Group Number NC content/% Reclaimed aggregate replacement rate/% Water-to-gel ratio test objective 1 0 50 0.40 Effect of NC doping 2 0.5 50 0.40 3 1.0 50 0.40 4 1.5 50 0.40 5 2.0 50 0.40 6 2.5 50 0.40 7 1.0 0 0.40 Effect of replacement rate of recycled aggregate 8 1.0 25 0.40 9 1.0 50 0.40 10 1.0 75 0.40 11 1.0 100 0.40 12 1.0 50 0.35 Effect of water-gel ratio 13 1.0 50 0.40 14 1.0 50 0.45 Orthogonal experimental design Based on the single-factor test results, three orthogonal factors were selected for optimization: NC admixture proportion (A), recycled aggregate replacement rate (B), and water-to-binder ratio (C), each with three levels. The L₉(3⁴) orthogonal design was employed to evaluate the RAC mix proportion using yield stress, plastic viscosity, and 28-day compressive strength as performance indicators. The orthogonal factor levels are detailed in Table 4 , while the experimental grouping is presented in Table 5 . Table 4 Orthogonal experimental factors and horizontal design. factor Horizontal 1 Horizontal 2 Level 3 A: NC content/% 0.8 1.2 1.6 B: Regenerated aggregate replacement rate/% 30 50 70 C: Water-to-cement ratio 0.38 0.40 0.42 Table 5 Experimental scheme arrangement based on L₉(3⁴) orthogonal table. test number A: NC content/% B: Regenerated aggregate replacement rate/% C: Water-to-cement ratio Empty column 1 1(0.8) 1(30) 1(0.38) 1 2 1(0.8) 2(50) 2(0.40) 2 3 1(0.8) 3(70) 3(0.42) 3 4 2(1.2) 1(30) 2(0.40) 3 5 2(1.2) 2(50) 3(0.42) 1 6 2(1.2) 3(70) 1(0.38) 2 7 3(1.6) 1(30) 3(0.42) 2 8 3(1.6) 2(50) 1(0.38) 3 9 3(1.6) 3(70) 2(0.40) 1 Test method Concrete mixing The concrete is prepared using a 60L forced-action mixer with the following sequence: ① Add pre-moistened recycled aggregates (or natural aggregates) and river sand to the mixer, dry mix for 30 seconds; ② Add NC powder and continue dry mixing for 30 seconds to ensure uniform dispersion; ③ Add cement and dry mix for 60 seconds; ④ Add 70% of the mixing water and water reducer, wet mix for 60 seconds; ⑤ Add the remaining 30% of mixing water and wet mix for 90 seconds. Immediately after mixing, perform rheological testing and specimen molding. Rheological performance test The rheological properties of fresh RAC were tested using a Brookfield R/S-SST rotational rheometer at 20 ± 2℃. The Bingham model was applied to fit the rheological curves, yielding yield stress (τ₀) and plastic viscosity (µ). The Bingham model equation is expressed as: τ = τ₀+µγ (where τ denotes shear stress and γ represents shear rate). Prior to testing, the probe was preheated to the experimental temperature. Fresh concrete was poured into the testing vessel and left undisturbed for 2 minutes to eliminate air bubbles. Subsequently, the test was conducted by increasing the shear rate from 0 s⁻¹ to 100 s⁻¹ and then decreasing it back to 0 s⁻¹. Data from the descending phase was collected for fitting analysis. Mechanical property testing Test specimens shall be prepared in accordance with the Standard for Testing Methods of Mechanical Properties of Ordinary Concrete (GB/T 50081 − 2019). For compressive strength testing, 100mm×100mm×100mm cubic specimens shall be used; for splitting-tensile strength testing, 100mm×100mm×100mm cubic specimens shall be employed; and for flexural strength testing, 100mm×100mm×400mm prism specimens shall be utilized. Three parallel specimens shall be prepared for each group. After molding, specimens shall be cured in a standard curing chamber (20 ± 2℃, relative humidity ≥ 95%) for 3d,7d, and 28d ages, and mechanical property tests shall be conducted using the YES-2000 pressure testing machine. The loading rates for compressive strength testing shall be 0.5 ~ 0.8MPa/s, splitting-tensile strength testing shall be 0.02 ~ 0.05MPa/s, and flexural strength testing shall be 0.05 ~ 0.08MPa/s. Micro performance testing (1) Scanning Electron Microscopy (SEM) Analysis: Concrete specimens aged 28 days were selected. Samples measuring 5mm×5mm×5mm were cut near the aggregate-mortar interface transition zone (ITZ). After dehydration through anhydrous ethanol immersion, the specimens were polished sequentially with 400#,800#,1200#, and 2000# sandpaper, followed by gold sputtering. Microstructural morphology and ITZ structure were observed using a ZEISS Sigma 300 SEM at 15kV acceleration voltage. (2) X-ray Diffraction (XRD) Analysis: Cement paste specimens aged 28 days were crushed and ground to particle sizes below 80µm. After drying at 105°C until constant weight, phase analysis was performed using a Bruker D8 Advance XRD instrument. Test conditions: Cu Kα target, 40kV tube voltage, 40mA tube current, scanning range 5°~60°, scanning rate 5°/min. (3) Mercury Porosimetry (MIP) Analysis: Concrete core specimens aged 28 days were prepared as 5mm diameter × 5mm height cylindrical specimens. After vacuum drying, pore structure was measured using an AutoPore IV 9500 mercury porometer. The test pressure range was 0.006 ~ 414MPa, with measurable pore sizes ranging from 3.7nm to 100µm. Experimental results and analysis Single factor test results and analysis Influence of NC content on RAC rheological and mechanical properties Figure 2 illustrates the influence of NC content on RAC's rheological properties. As shown in Fig. 2 (a), when NC content increases from 0% to 1.5%, the yield stress of RAC decreases from 87.6Pa to 60.8Pa, representing a 30.6% reduction. However, beyond 1.5%, the yield stress begins to rise, reaching 79.2Pa at 2.5% content. This phenomenon occurs because low-content NC particles disperse uniformly, effectively filling micro-pores in the cement paste and reducing inter-particle friction, thereby lowering the yield stress. Conversely, high-content NC particles exhibit higher surface energy, leading to agglomeration that increases internal friction resistance within the paste, ultimately elevating the yield stress. As shown in Fig. 2 (b), the variation trend of plastic viscosity aligns with the yield stress: When the NC content ranges from 0% to 1.5%, the plastic viscosity decreases from 32.4Pa·s to 24.1Pa·s, representing a 25.6% reduction. However, when the content exceeds 1.5%, the plastic viscosity increases with further addition. This phenomenon occurs because NC particles act as "ball bearings" between cement particles, reducing the flow resistance of the paste. Conversely, the formation of agglomerates disrupts this "ball bearing effect" while simultaneously increasing the paste's viscosity. Figure 3 illustrates the influence of NC content on the mechanical properties of RAC. As shown in the figure, the compressive strength at 3d,7d, and 28d all initially increased and then decreased with rising NC content, reaching peak values at 1.5% NC content. Specifically, the 28-day compressive strength increased from 42.4MPa in the control group to 53.7MPa, representing a 26.7% improvement. The 3d and 7d compressive strengths showed increases of 29.8% and 27.3%, respectively. The trends for splitting tensile strength and flexural strength mirrored those of compressive strength: At 1.5% NC content, the 28-day splitting tensile strength reached 3.8MPa (26.7% increase), while the flexural strength achieved 6.5MPa (22.6% increase). The enhanced mechanical strength of low-NC-cement mixtures primarily stems from two mechanisms: First, the nucleation effect of NC accelerates cement hydration, generating more C-S-H gel and refining the microstructure. Second, the filling effect reduces internal porosity and improves density. When NC content exceeds 1.5%, agglomerates form internal defects that induce stress concentration under external forces, leading to strength reduction! Based on rheological and mechanical performance evaluations, the optimal NC!! content range is 1.0%–1.5%. Effect of regenerated aggregate replacement rate on rheological and mechanical properties of RAC Figure 4 illustrates the impact of recycled aggregate replacement rates on the rheological properties of RAC. As shown in Fig. 4 , when the recycled aggregate replacement rate increases from 0% to 100%, the yield stress rises from 65.2Pa to 112.8Pa, representing a 73.0% increase, while plastic viscosity rises from 25.8Pa·s to 41.2Pa·s, showing a 59.7% improvement. This is attributed to the rough surface and sharp edges of recycled aggregates, which adhere to hardened cement mortar and increase frictional resistance between aggregates and the paste. Additionally, the high water absorption capacity of recycled aggregates draws free water from the paste, leading to increased viscosity and degraded flowability. When the replacement rate is below 50%, the deterioration in rheological properties occurs gradually. However, when exceeding 50%, the deterioration accelerates significantly, primarily due to the cumulative effect of defects in recycled aggregates becoming more pronounced. Figure 5 illustrates the impact of recycled aggregate replacement rates on the mechanical properties of RAC. The results demonstrate a consistent decline in mechanical strength as the replacement rate increases: From 0% to 100%, the 28-day compressive strength drops from 50.2MPa to 35.6MPa (29.1% decrease), tensile strength decreases from 3.9MPa to 2.6MPa (33.3% reduction), and flexural strength declines from 6.8MPa to 4.7MPa (30.9% decrease). The primary reasons for this strength reduction include: ① Recycled aggregates exhibit lower inherent strength than natural aggregates, with crushing index values 1.8 times lower (Table 2 ), resulting in reduced load-bearing capacity; ② A weak interfacial transition zone (ITZ) forms between recycled aggregate surface cement mortar and fresh mortar, prone to microcracking; ③ The high porosity of recycled aggregates reduces concrete density. When the replacement rate reaches 50%, the 28-day compressive strength still achieves 43.8MPa, meeting C40 concrete requirements. Given the high utilization rate of recycled aggregates, a 50% replacement rate proves optimal for balancing performance and cost-effectiveness. Influence of water-to-cement ratio on RAC rheological and mechanical properties Figure 6 illustrates the influence of water-to-cement ratio on RAC's rheological properties. As shown in the figure, when the water-to-cement ratio increases from 0.35 to 0.45, the yield stress decreases from 98.5Pa to 52.3Pa, representing a 46.9% reduction, while plastic viscosity drops from 38.6Pa·s to 21.4Pa·s, showing a 44.6% decrease. This improvement is attributed to the increased free water content in the paste, enhanced cement particle dispersion, reduced inter-particle cohesion, and decreased flow resistance, which collectively lead to significant enhancements in rheological performance. However, when the water-to-cement ratio exceeds 0.45, fresh concrete becomes prone to segregation and water bleeding, compromising construction quality. Conversely, a ratio below 0.35 results in excessively viscous paste, making concrete placement more challenging. Figure 7 illustrates the influence of water-to-cement ratio on RAC mechanical properties. As shown in the figure, mechanical strength demonstrates a significant decline with increasing water-to-cement ratio: When the ratio rises from 0.35 to 0.45, the 28-day compressive strength decreases from 56.3MPa to 39.8MPa, representing a 29.3% reduction; the splitting tensile strength drops from 4.2MPa to 3.0MPa (28.6% decrease); and the flexural strength diminishes from 7.1MPa to 5.2MPa (26.8% reduction). This phenomenon occurs because higher water-to-cement ratios reduce the density of cement hydration products, increase internal porosity, and allow residual moisture to evaporate, leaving more voids that form stress concentration sources. Comprehensive rheological and mechanical analysis indicates that at a water-to-cement ratio of 0.40, RAC achieves optimal performance with a yield stress of 72.5Pa and plastic viscosity of 28.3Pa·s, meeting construction workability requirements while attaining a 28-day compressive strength of 48.6MPa. Orthogonal test results and optimization analysis Orthogonal test results The rheological and mechanical property test results of the orthogonal experiment are presented in Table 6 . Using yield stress (lower is better), plastic viscosity (lower is better), and 28-day compressive strength (higher is better) as evaluation indicators, the mix design was optimized through a comprehensive scoring method. The scoring calculation method involves standardizing each indicator's test value to a 0-100 point scale: yield stress and plastic viscosity undergo reverse standardization (lower values receive higher scores), while compressive strength adopts forward standardization (higher values receive higher scores). Based on engineering requirements, the weights assigned to yield stress, plastic viscosity, and compressive strength are 0.3, 0.2, and 0.5, respectively. The comprehensive score is calculated as: (yield stress score × 0.3) + (plastic viscosity score × 0.2) + (compressive strength score × 0.5). Table 6 L₉(3⁴) orthogonal experiment test results and comprehensive score. Test number NC content/% Reclaimed aggregate replacement rate/% Water-to-gel ratio Yield stress /Pa Viscosity (Pa·s) 28d compressive strength/MPa Overall score 1 0.8 30 0.38 78.6 29.4 50.3 82.5 2 0.8 50 0.40 72.3 27.6 49.8 84.2 3 0.8 70 0.42 89.5 33.2 45.6 73.1 4 1.2 30 0.40 65.2 24.5 52.1 89.6 5 1.2 50 0.42 75.8 28.3 50.5 83.8 6 1.2 70 0.38 82.4 30.1 48.2 79.3 7 1.6 30 0.42 79.3 31.5 49.7 80.1 8 1.6 50 0.38 73.6 28.8 51.2 85.4 9 1.6 70 0.40 92.7 34.6 44.3 71.5 Range and variance analysis To assess the significance of each factor's impact on evaluation indicators, range analysis and ANOVA were performed on the orthogonal test results (Tables 7 and 8 ). In range analysis, a larger R value indicates a more significant factor effect. For ANOVA, higher F values and lower P values demonstrate greater significance (P < 0.05 indicates significant effect, P < 0.01 indicates highly significant effect). Table 7 The range analysis results of the influence of various factors on different evaluation indicators. Evaluating indicator factor Horizontal 1 Mean Horizontal 2 Mean Horizontal 3 Mean Range R Impact order Yield stress /Pa A (NC content) 80.1 74.5 81.9 7.4 B > C > A B (Replacement rate) 74.4 73.9 88.2 14.3 C (water-to-cement ratio) 78.2 77.4 80.9 3.5 Viscosity (Pa·s) A (NC content) 30.1 27.6 31.6 4.0 B > A > C B (Replacement rate) 28.5 27.6 34.9 7.3 C (water-to-cement ratio) 29.4 28.8 30.9 2.1 28d compressive strength/MPa A (NC content) 48.6 50.3 48.4 1.9 B > A > C B (Replacement rate) 50.7 50.5 46.0 4.7 C (water-to-cement ratio) 49.9 48.7 48.7 1.2 Overall score A (NC content) 79.9 84.2 78.7 5.5 B > A > C B (Replacement rate) 84.1 84.5 74.6 9.9 C (water-to-cement ratio) 82.4 81.8 78.6 3.8 Table 8 The results of the variance analysis of the comprehensive score. Source of variation Sum of Squares free degree mean square F price P price conspicuousness A (NC content) 48.62 2 24.31 15.23 0.028 notable B (Replacement rate) 126.35 2 63.18 39.65 0.005 Highly significant C (water-to-cement ratio) 21.58 2 10.79 6.77 0.083 quiet Error 3.19 2 1.60 - - - Sum 199.74 8 - - - - As shown in Tables 7 and 8 : ① The replacement rate of recycled aggregates (B) significantly affects the composite score (P = 0.005), being the primary factor influencing RAC performance; ② NC content (A) shows significant influence (P = 0.028), ranking as a secondary factor; ③ Water-to-binder ratio (C) demonstrates no significant effect (P = 0.083). Based on the average levels of all factors, the optimal mix design is A₂B₂C₂, comprising 1.2% NC content, 50% recycled aggregates, and a water-to-binder ratio of 0.40. Optimal mix ratio verification test To validate the reliability of the optimal mix design, three test specimens were prepared: (1) an optimal mix specimen (A₂B₂C₂: 1.2% NC content, 50% recycled aggregate replacement, water-to-binder ratio 0.40), (2) a control specimen (0% NC content, 0% recycled aggregate replacement), and (3) an orthogonal test specimen from Group 4 (A₂B₁C₂: 1.2% NC content, 30% recycled aggregate replacement, water-to-binder ratio 0.40). Their rheological and mechanical properties were compared, with the results presented in Table 9 . Table 9 The verification results of rheological and mechanical properties of the optimal mix ratio and the control group. Group NC content/% Reclaimed aggregate replacement rate/% Water-to-gel ratio yield stress /Pa Viscosity (Pa·s) 3d compressive strength/MPa 7d compressive strength/MPa 28d compressive strength/MPa Baseline group 0 0 0.40 76.8 29.7 32.5 41.2 49.6 Orthogonal Group 4 1.2 30 0.40 65.2 24.5 35.8 45.6 52.1 Best mix ratio group 1.2 50 0.40 68.4 25.9 34.6 44.3 52.8 As shown in Table 9 : ① Although the yield stress (68.4Pa) and plastic viscosity (25.9Pa·s) of the optimal mix design slightly exceed those of Orthogonal Group 4, they are significantly lower than the reference group (reduced by 10.9% and 12.8% respectively), meeting the pumping construction requirements for fresh concrete rheological properties (yield stress 50–80 Pa, plastic viscosity 20–30 Pa·s); ② In terms of mechanical properties, the optimal mix achieved a 28-day compressive strength of 52.8MPa, representing a 6.5% improvement over the reference group and a 1.3% increase compared to Orthogonal Group 4. The 3-day and 7-day compressive strengths also outperformed the reference group, with improvements ranging from 6.5% to 7.3%; ③ Compared to Orthogonal Group 4 with a 30% recycled aggregate replacement rate, the optimal mix increased recycled aggregate utilization to 50%, significantly enhancing solid waste resource efficiency while maintaining performance, aligning with green building development needs. Verification results demonstrate that the optimal mix achieves excellent rheological properties, mechanical performance, and cost-effectiveness, confirming the reliability of the optimization outcomes. Micro performance analysis To investigate the modification mechanism of NC on RAC, three groups were selected for SEM, XRD, and MIP analysis: the control group, the optimal mix ratio group, and the recycled aggregate concrete group without NC (RA50 group: 50% recycled aggregate replacement, 0% NC addition, water-to-binder ratio 0.40). The study aimed to analyze the changes in microstructure, phase composition, and pore structure. SEM microstructure analysis Figure 8 presents SEM images of three concrete groups at 28-day age. As shown in Fig. 8 (a) of the reference group, the interface transition zone (ITZ) between natural aggregates and cement paste exhibits a dense structure with minimal micro-pores, while the C-S-H gel displays fibrous interwoven distribution – this microstructural foundation explains the superior mechanical properties of the reference group. In contrast, Fig. 8 (b) of the RA50 group reveals significant ITZ cracks and voids (2–5µm wide), with the C-S-H gel appearing as loose flocculent aggregates. The poor bond between recycled aggregates and newly applied mortar creates a "double interface" defect, which aligns with the macroscopic observation of its 28-day compressive strength being only 42.4MPa (14.5% lower than the reference group). Figure 8 (c) demonstrates significant improvements in the microstructure of the optimal mix design: ① ITZ region cracks have virtually disappeared, with their width reduced to below 0.5µm, and aggregates are tightly bonded with the cement paste; ② The C-S-H gel forms a dense network structure that fills the pores; ③ NC particles are uniformly dispersed in the paste without noticeable agglomeration, with some NC particles serving as nuclei encapsulated by the C-S-H gel. This is attributed to the dual effects of NC's interface modification enhancing ITZ's bonding strength and its nucleation effect promoting C-S-H gel formation. These combined mechanisms reduce microstructural defects and improve macroscopic mechanical properties. XRD phase composition analysis Figure 9 presents XRD patterns of three concrete cement paste groups. All three spectra exhibit characteristic diffraction peaks of Ca(OH)₂, C₃S, C₂S, and calcite (CaCO₃), with the calcite peak primarily originating from carbonation of NC and cement hydration products. Compared to the reference group and RA50 group, the optimal mix ratio group shows a significant 23.8% reduction in the intensity of CH's characteristic diffraction peaks (2θ = 18.0°,34.1°), while the intensity of C-S-H gel's characteristic diffuse peaks (2θ = 20°~30°) markedly increases. CH, a product of cement hydration, can cause internal alkalinity imbalance in concrete when present in excess. Its plate-like crystalline structure tends to align directionally in ITZ regions, forming weak points. The reduced CH content in the optimal mix ratio group results from NC particles acting as nuclei that promote C₃S and C₂S hydration to generate more C-S-H gel, while simultaneously consuming part of CH and reducing its enrichment in ITZ. XRD results confirm NC's nucleation effect, demonstrating that optimizing the composition of hydration products enhances concrete's microstructure. MIP pore structure analysis Concrete's macroscopic properties are closely related to its pore structure. Lower porosity and a higher proportion of non-hazardous pores (with pore size < 20nm) result in superior mechanical properties and durability. Table 10 presents the MIP test results for three concrete groups, while Fig. 10 shows the pore size distribution curve. Table 10 Comparison of concrete pore structure parameters in each group (MIP method). Group Total porosity/% Non-hazardous holes ( 200nm) proportion/% Baseline group 12.8 35.2 28.6 22.4 13.8 RA50 Group 18.5 22.1 25.3 30.5 22.1 Best mix ratio 13.2 41.5 30.2 18.8 9.5 As shown in Table 10 : ① The RA50 group achieved a total porosity of 18.5%, representing a 44.5% increase compared to the reference group, with harmful and multi-harmful pores accounting for 52.6% – the primary cause of its mechanical deterioration; ② The optimal mix proportion group reduced total porosity to 13.2%, slightly higher than the reference group but 28.6% lower than RA50; ③ The optimal mix proportion group increased harmless pore proportion to 41.5% while decreasing multi-harmful pores to 9.5%, demonstrating significant pore size distribution optimization. These results validate NC's filling effect: NC particles (30-80nm) effectively fill capillary pores (50-200nm) in cement paste, refine pore sizes, convert some harmful pores into harmless ones, and reduce water and harmful substance penetration pathways, thereby enhancing concrete density and mechanical strength. Modification mechanism analysis By integrating macroscopic performance with microscopic test results, NC's modification effect on RAC is achieved through three synergistic mechanisms: filling effect, nucleation effect, and interface modification. (1) Filling Effect: With particle sizes of 30–80 nm, NC particles effectively fill micro-pores in cement paste, voids on recycled aggregate surfaces, and ITZ regions. This reduces macroscopic defects, refines pore size distribution, lowers total porosity (Table 10 ), and enhances concrete density. The filling effect directly improves both fresh concrete's rheological properties (reducing particle friction) and hardened concrete's mechanical performance (minimizing stress concentration). (2) Nucleation Effect: NC's surface contains abundant active sites that adsorb Ca²⁺ and SiO₄⁴⁻ ions from cement hydration. These ions act as nucleation sites for C-S-H gel formation, promoting C₃S and C₂S hydration (as evidenced by reduced CH content and increased C-S-H gel in XRD analysis). The resulting C-S-H gel forms a network-like structure that strengthens inter-particle bonding while filling pores, optimizing the microstructure. (3) Interface Modification: The "dual interface" of recycled aggregates remains a weak point in RAC. NC enhances interface performance through two pathways: ① Adsorption of NC particles on aggregate surfaces improves physical bonding between paste and aggregate; ② NC promotes C-S-H gel formation in ITZ regions, reducing CH crystal orientation and eliminating interface cracks (SEM image 8), thereby transforming ITZ from a "weak zone" to a "strengthened zone". Three synergistic effects work in tandem: The filling effect creates a dense reaction environment for nucleation, while the hydration products generated by nucleation enhance the filling effect. Interface modification improves the structural load-bearing capacity, ultimately achieving synergistic optimization of RAC's rheological and mechanical properties. Conclusions and outlook The effects of NC dosage, recycled aggregate substitution rate, and water-to-cement ratio on RAC performance are significant and follow clear patterns: ① Performance peaks at NC dosage of 1.0%~1.5%, while excessive dosage causes performance degradation due to agglomeration; ② Recycled aggregate substitution rate shows negative correlation with RAC performance, with 50% being the optimal balance point for both performance and cost-effectiveness; ③ Rheological and mechanical properties achieve optimal synergy at water-to-cement ratio of 0.40. Orthogonal experiments optimized the best RAC mix design: NC dosage 1.2%, recycled aggregate substitution rate 50%, water-to-cement ratio 0.40. Under this mix design, RAC exhibits yield stress 68.4Pa and plastic viscosity 25.9Pa·s, meeting construction requirements; 28-day compressive strength reaches 52.8MPa, 6.5% higher than the reference group and 24.5% higher than the NC-free RA50 group. NC synergistically modifies RAC through three effects: pore-filling (refining pores), nucleation (promoting C-S-H gel formation), and interface modification (strengthening ITZ). The interface modification effect addresses the "double interface" defect, while nucleation and pore-filling further optimize microstructure to enhance macroscopic performance. This NC-modified RAC technology proposed in this study achieves 50% recycled aggregate utilization while maintaining C40 concrete performance, providing an economically viable solution for construction solid waste recycling. Aligning with "dual carbon" goals and green building concepts, it can be widely applied in municipal engineering and residential building load-bearing structures. Future research could focus on the following directions: ① Investigate the synergistic effects of NC with other modifiers to further enhance RAC performance; ② Conduct long-term durability tests to clarify the performance evolution patterns of NC-modified RAC under harsh conditions such as freeze-thaw cycles and chloride salt erosion; ③ Explore the hydration heat release patterns and volume deformation characteristics of NC-modified RAC to provide a basis for large-volume concrete construction. Declarations Acknowledgements None. Funding: This research was funded by the financial support from the Science and technology project of Zhejiang Huadong Geotechnical Investigation & Design Institute CO, Ltd (KY2019-XNY-03-06, KY2021-XNY-03-02, KY2024-XNY-03-01). Author contributions Data curation, Xu Jun; Funding acquisition and Investigation, Lyu Guang-hua; Methodology and Project administration, Tan Min; Resources,Tan Min; Supervision, Lyu Guang-hua; Writing—original draft, Xu Jun; Writing—review & editing, Xu Jun. All authors read and approved the final manuscript. Additional information Competing interests The author(s) declare no competing interests. Data availability statement All data generated or analysed during this study are included in this published article. References Feng, C., Cui, B., Ge, H., Huang, Y. & Zhang, W. Reinforcement of recycled aggregate by microbial-induced mineralization and deposition of calcium carbonate—influencing factors, mechanism and effect of reinforcement. Crystals 11 , 887. https://doi.org/10.3390/cryst11080887 (2021). Xiao, J., Deng, Q., Duan, Z., Hou, S. & Tao, J. Carbonization modification of recycled fine aggregates and its influence on the rheological properties of mortar. J. Appl. Basic. Sci. Eng. 32 , 1486–1495. https://doi.org/10.16058/j.issn.1005-0930.2024.05.021 (2024). Dan, Y., Liang, Y., Xu, R., Ning, F. & Chen, Z. Experimental study on the early mechanical properties of recycled aggregate concrete after carbonation of NaHCO₃. J. Compos. Mater. 42 , 3371–3383. https://doi.org/10.13801/j.cnki.fhclxb.20240903.006 (2025). Zhang, M., Ding, Y., Yang, X. & Sun, B. Mechanical properties and strengthening mechanism of nano-SiO₂ composite carbonized fully recycled aggregate concrete. J. Compos. Mater. 42 , 2102–2111. https://doi.org/10.13801/j.cnki.fhclxb.20240522.007 (2025). Chen, Z., Zhang, Y., Chen, J. & Fan, J. Sensitivity factors analysis on the compressive strength and flexural strength of recycled aggregate infill wall materials. Appl. Sci. 8 , 1090. https://doi.org/10.3390/app8071090 (2018). Li, G. et al. Acoustic emission characteristics and damage mechanisms investigation of basalt fiber concrete with recycled aggregate. Materials 13 , 4009–4031. https://doi.org/10.3390/ma13184009 (2020). Zhang, J., Zhou, Z. & Cheng, X. Formation kinetics of regenerated cement clinker calcined by using wasted recycling concrete powders as raw meals. Adv. Mater. Res. 1073–1076 , 1309–1312. https://doi.org/10.4028/www.scientific.net/amr.1073-1076.1309 (2015). Zheng, L. & Pang, J. Basic mechanical properties of recycled concrete aggregate the impact study. J. Shanxi Norm Univ. 39 , 78–82. https://doi.org/10.16207/j.cnki.1009-4490.2025.03.004 (2025). Zhong, C. et al. Recycled fine aggregate mortar of carbide and the influence of mechanical properties of concrete. J. Silic Bull. 44 , 1468–1476. https://doi.org/10.16552/j.cnki.issn1001-1625.2024.1402 (2025). Zhang, X., Jiang, X., Liu, Y. & Deng, H. Orthogonal experiment and numerical simulation of influencing factors on compressive strength of recycled aggregate concrete. Hydro Energy Sci. 43 , 93–98. https://doi.org/10.20040/j.cnki.1000-7709.2025.20240333 (2025). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 20 Apr, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 16 Jan, 2026 Reviews received at journal 15 Jan, 2026 Reviews received at journal 14 Jan, 2026 Reviewers agreed at journal 04 Jan, 2026 Reviewers agreed at journal 03 Jan, 2026 Reviewers agreed at journal 02 Jan, 2026 Reviewers agreed at journal 02 Jan, 2026 Reviewers agreed at journal 02 Jan, 2026 Reviewers invited by journal 02 Jan, 2026 Editor invited by journal 02 Jan, 2026 Editor assigned by journal 29 Dec, 2025 Submission checks completed at journal 29 Dec, 2025 First submitted to journal 24 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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2","display":"","copyAsset":false,"role":"figure","size":275401,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of NC content on RAC rheological properties.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/d4f45cc9140c6f080021693c.png"},{"id":99790883,"identity":"70bfeeba-bd65-4fe7-bc3e-94f5304bbad9","added_by":"auto","created_at":"2026-01-08 12:58:48","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":325694,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of NC content on mechanical properties of RAC.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/0d89ac164d7f0ba4c206de2d.png"},{"id":99511549,"identity":"f7adfac1-fdfd-4bec-bf86-f108d0908292","added_by":"auto","created_at":"2026-01-05 09:37:52","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":414085,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of recycled aggregate replacement rate on RAC rheological properties.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/e99ad8c3a0da0ca36307b76f.png"},{"id":99791648,"identity":"2bf50654-5a16-40dc-8703-05751dd1d96c","added_by":"auto","created_at":"2026-01-08 13:06:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":616823,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of recycled aggregate replacement rate on RAC mechanical properties.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/7baf652691580477cdbcd51b.png"},{"id":99790803,"identity":"9dbb5bb3-1eb7-4f7c-aed3-c6e1496ba3d5","added_by":"auto","created_at":"2026-01-08 12:58:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":369655,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of water-to-binder ratio on RAC rheological properties.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/ab3dbef261cd364034308eb7.png"},{"id":99791260,"identity":"fbb5d796-5324-4657-af8a-dc18efcd456f","added_by":"auto","created_at":"2026-01-08 12:59:22","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":467459,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of water-to-binder ratio on mechanical properties of RAC.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/4f302c82aada7c591d54ec51.png"},{"id":99792044,"identity":"68d90912-13e2-4d78-bec6-1dabea05afbb","added_by":"auto","created_at":"2026-01-08 13:12:55","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":395052,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of concrete specimens from different groups.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/505f37510edb4173c56c70c9.png"},{"id":99511551,"identity":"5a4d642d-b463-488c-9c74-ea540db78060","added_by":"auto","created_at":"2026-01-05 09:37:53","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":486421,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of concrete from different groups.\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/4f567b928142593d0c107b2c.png"},{"id":107927911,"identity":"34225fc2-8f30-4f1e-b82e-8c0aa2141510","added_by":"auto","created_at":"2026-04-27 16:06:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4213650,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8439637/v1/926ee6b6-ae9c-4992-bb23-2427865445fc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on rheological and mechanical properties optimization and mechanism of Nano-CaCO₃ regenerated aggregate concrete","fulltext":[{"header":"Introduction","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003eResearch background and significance\u003c/h2\u003e \u003cp\u003eWith the acceleration of urbanization and infrastructure upgrades in China, over 3\u0026nbsp;billion tons of construction solid waste are generated annually, with discarded concrete accounting for more than 40% of this total\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e. As a core product of recycled concrete resource utilization, recycled aggregate (RA) and its resulting recycled aggregate concrete (RAC) effectively reduce natural aggregate extraction and solid waste storage, aligning with the \"dual carbon\" goals and green building development concepts\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, recycled aggregates, having undergone hydration hardening and fragmentation processes in original concrete, exhibit rough, porous surfaces with sharp edges and substantial hardened cement mortar layers. These characteristics result in RAC's poor rheological properties (low fluidity, tendency to segregate), insufficient mechanical strength, and inadequate durability, severely limiting its application in load-bearing structures\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eNanomaterials demonstrate significant potential in concrete modification due to their size effects, surface effects, and quantum effects\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Nano-Calcium Carbonate (NC), a low-cost and easily dispersible nanomodifier with particle sizes typically ranging from 20 to 100 nm, can refine concrete internal pores through the filling effect and accelerate cement hydration via the nucleation effect, thereby improving both microstructure and macroscopic properties\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. While existing studies have shown NC's ability to enhance compressive strength and water resistance in ordinary concrete\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e, research on its synergistic optimization of rheological and mechanical properties in Regenerated Aggregate Concrete (RAC) remains limited. Particularly, there is a lack of comprehensive analysis of performance mechanisms under multi-factor interactions including NC dosage, recycled aggregate substitution rates, and water-to-binder ratios. Rheological properties directly determine RAC's workability and casting quality, while mechanical properties serve as the core indicator of structural load-bearing capacity. The synergistic optimization of these two aspects is crucial for achieving engineering applications of RAC\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Therefore, systematically investigating NC's influence on RAC's rheology and mechanical properties, optimizing mix proportions, and elucidating modification mechanisms holds significant theoretical and practical value for promoting efficient utilization of recycled aggregate resources and expanding RAC's application scenarios.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eState of research at home and abroad\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003ePerformance defects and modification of regenerated aggregate concrete\u003c/h2\u003e \u003cp\u003eThe \"dual interface\" characteristics of recycled aggregates (interface between recycled aggregates and adherent mortar, and between adherent mortar and fresh mortar) are the primary cause of RAC performance degradation. Li et al. found that when the recycled aggregate replacement rate increased from 0% to 100%, the 28-day compressive strength of RAC decreased by 15% to 30%, while the yield stress increased by over 40%, mainly due to the high water absorption rate of recycled aggregates causing increased viscosity of fresh concrete paste. To improve RAC performance, scholars have proposed physical modification methods (such as aggregate pretreatment and mechanical grinding) and chemical modification methods (such as adding mineral admixtures and chemical additives). Among these, Zhang Shuai et al. modified RAC using silica fume. When the silica fume dosage was 10%, the 28-day compressive strength increased by 18.2%, but the high specific surface area of silica fume tends to reduce concrete fluidity, requiring the use of high-efficiency water reducers.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eResearch on the application of Nano-CaCO₃ in concrete\u003c/h3\u003e\n\u003cp\u003eThe modified effects of NC in concrete are primarily manifested in three aspects: First, the filling effect, where NC particles fill capillary pores in cement paste and refine pore size distribution; Second, the nucleation effect, where active sites on NC surfaces adsorb cement hydration products to promote C-S-H gel formation; Third, the interface modification effect, where NC improves the structure of the interface transition zone between aggregates and cement paste, reducing interface cracks. Wang et al. demonstrated that when NC content reaches 1.0%, the 28-day compressive strength of ordinary concrete increases by 22.3% while porosity decreases by 14.5%. However, research on NC application in RAC still has limitations: On one hand, existing studies predominantly focus on mechanical properties while neglecting rheological performance, which is crucial for RAC construction quality; On the other hand, there is a lack of multi-factor interaction studies for performance optimization, making it challenging to directly guide engineering practices.\u003c/p\u003e\n\u003ch3\u003eResearch gaps and the scope of this study\u003c/h3\u003e\n\u003cp\u003eCurrent research on NC-modified RAC reveals three key gaps: (1) The complex interplay between NC dosage, recycled aggregate substitution rate, and water-to-binder ratio on RAC's rheological and mechanical properties remains unclear; (2) Systematic investigation of NC's microstructural mechanisms for enhancing RAC's rheological performance is lacking; (3) Optimization methods that balance both rheological and mechanical properties are still absent. To address these issues, this study systematically investigates the effects of NC dosage, recycled aggregate substitution rate, and water-to-binder ratio on RAC's rheological properties (yield stress, plastic viscosity) and mechanical properties (compressive strength, tensile strength, flexural strength) through single-factor and orthogonal experiments. Using SEM, XRD, and MIP as microscopic characterization tools, we elucidate NC's modification mechanisms. The research ultimately proposes an optimal NC-modified RAC mix design that balances rheological and mechanical performance, providing a theoretical foundation for NC's engineering applications in RAC.\u003c/p\u003e"},{"header":"Experimental materials and methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eTest materials\u003c/h2\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eGelation materials\u003c/h2\u003e \u003cp\u003eOrdinary Portland cement (OPC) with P·O 42.5 grade is adopted, whose performance indexes meet the requirements of \"General Portland Cement\" (GB 175–2007), and the main performance indexes are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\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\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\u003eMain performance indicators of P·O 42.5 cement.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFineness (80µm sieve residue)/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003einitial setting time /min\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSettling time (min)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3D compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e28d compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3D flexural strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28d flexural strength/MPa\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e185\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e240\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e48.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7.2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eNano CaCO₃\u003c/h3\u003e\n\u003cp\u003eThe industrial-grade nano CaCO₃ powder (30-80nm particle size, ≥ 99% purity, 35-45m²/g specific surface area) was prepared. Its XRD pattern (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) shows predominantly calcite-type CaCO₃ with excellent crystallinity. To enhance dispersion, the powder was ultrasonically dispersed for 10 minutes using a 200W,40kHz ultrasonic disperser.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eAggregates\u003c/h2\u003e \u003cp\u003eNatural Aggregate (NA): Coarse aggregate consists of limestone crushed stone with continuous 5-20mm gradation, featuring an apparent density of 2780 kg/m³, bulk density of 1650 kg/m³, and clay content of 0.3%. Fine aggregate is river sand with a fineness modulus of 2.6, apparent density of 2650 kg/m³, bulk density of 1580 kg/m³, and clay content of 1.2%, meeting the requirements of \"Sand for Construction\" (GB/T 14684 − 2022). Regenerated Aggregate (RA): Made from 20-year-old discarded reinforced concrete beams, this recycled coarse aggregate undergoes crushing and screening to produce continuous 5-20mm gradation. Its performance indicators are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. According to \"Regenerated Coarse Aggregate for Concrete\" (GB/T 25177 − 2010), this recycled aggregate is classified as Class II.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\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\u003eMain performance indicators of recycled coarse aggregates (Class II).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApparent density (kg/m³)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBulk density (kg/m³)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ewater absorption /%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003esediment percentage /%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCrush Indicator/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAdhesive mortar content/%\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2450\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1520\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.6\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eAdditives and water\u003c/h2\u003e \u003cp\u003eThe product employs a polycarboxylate-based high-efficiency water reducer with a solid content of 40% and a water reduction rate of ≥ 30%, meeting the requirements of 'Concrete Admixtures' (GB 8076 − 2008). The test water is tap water.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eTest protocol\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003eDesign principles for mix proportions\u003c/h2\u003e \u003cp\u003eUsing C40 concrete as the reference, the baseline mix design (0% NC admixture and 0% recycled aggregate replacement rate) consists of: cement 420 kg/m³, natural coarse aggregate 1180 kg/m³, river sand 650 kg/m³, water 168 kg/m³, and water reducer 1.2% (as a percentage of cementitious material mass). To mitigate the high water absorption characteristics of recycled aggregates, a 24-hour pre-wetting treatment was applied prior to use, maintaining a surface moisture content of 2%. The experimental variables included: NC admixture levels (0%,0.5%,1.0%,1.5%,2.0%,2.5% based on cementitious material mass), recycled aggregate replacement rates (0%,25%,50%,75%,100% based on total coarse aggregate mass), and water-cement ratio (0.35,0.40,0.45).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eSingle factor test design\u003c/h2\u003e \u003cp\u003eThe single-factor experiment was conducted to evaluate the impact of a single variable on RAC performance, with experimental groups as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Specifically, Groups 1–6 maintained a 50% recycled aggregate replacement rate and water-to-binder ratio of 0.40 while varying the NC content; Groups 7–11 kept the NC content at 1.0% and water-to-binder ratio at 0.40 while adjusting the recycled aggregate replacement rate; Groups 12–14 fixed the NC content at 1.0% and recycled aggregate replacement rate at 50%, while modifying the water-to-binder ratio.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\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\u003eSingle-factor experimental design scheme and grouping parameters.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTrial Group Number\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNC content/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReclaimed aggregate replacement rate/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWater-to-gel ratio\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003etest objective\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003eEffect of NC doping\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eEffect of replacement rate of recycled aggregate\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e75\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eEffect of water-gel ratio\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eOrthogonal experimental design\u003c/h2\u003e \u003cp\u003eBased on the single-factor test results, three orthogonal factors were selected for optimization: NC admixture proportion (A), recycled aggregate replacement rate (B), and water-to-binder ratio (C), each with three levels. The L₉(3⁴) orthogonal design was employed to evaluate the RAC mix proportion using yield stress, plastic viscosity, and 28-day compressive strength as performance indicators. The orthogonal factor levels are detailed in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, while the experimental grouping is presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\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\u003eOrthogonal experimental factors and horizontal design.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003efactor\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHorizontal 1\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHorizontal 2\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLevel 3\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA: NC content/%\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB: Regenerated aggregate replacement rate/%\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC: Water-to-cement ratio\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"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\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\u003eExperimental scheme arrangement based on L₉(3⁴) orthogonal table.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003etest number\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA: NC content/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB: Regenerated aggregate replacement rate/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC: Water-to-cement ratio\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEmpty column\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1(0.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1(30)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(0.38)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1(0.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2(50)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2(0.40)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1(0.8)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3(70)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3(0.42)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2(1.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1(30)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2(0.40)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2(1.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2(50)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3(0.42)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2(1.2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3(70)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(0.38)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3(1.6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1(30)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3(0.42)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3(1.6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2(50)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1(0.38)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3(1.6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3(70)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2(0.40)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eTest method\u003c/h2\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003eConcrete mixing\u003c/h2\u003e \u003cp\u003eThe concrete is prepared using a 60L forced-action mixer with the following sequence: ① Add pre-moistened recycled aggregates (or natural aggregates) and river sand to the mixer, dry mix for 30 seconds; ② Add NC powder and continue dry mixing for 30 seconds to ensure uniform dispersion; ③ Add cement and dry mix for 60 seconds; ④ Add 70% of the mixing water and water reducer, wet mix for 60 seconds; ⑤ Add the remaining 30% of mixing water and wet mix for 90 seconds. Immediately after mixing, perform rheological testing and specimen molding.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eRheological performance test\u003c/h2\u003e \u003cp\u003eThe rheological properties of fresh RAC were tested using a Brookfield R/S-SST rotational rheometer at 20 ± 2℃. The Bingham model was applied to fit the rheological curves, yielding yield stress (τ₀) and plastic viscosity (µ). The Bingham model equation is expressed as: τ = τ₀+µγ (where τ denotes shear stress and γ represents shear rate). Prior to testing, the probe was preheated to the experimental temperature. Fresh concrete was poured into the testing vessel and left undisturbed for 2 minutes to eliminate air bubbles. Subsequently, the test was conducted by increasing the shear rate from 0 s⁻¹ to 100 s⁻¹ and then decreasing it back to 0 s⁻¹. Data from the descending phase was collected for fitting analysis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eMechanical property testing\u003c/h2\u003e \u003cp\u003eTest specimens shall be prepared in accordance with the Standard for Testing Methods of Mechanical Properties of Ordinary Concrete (GB/T 50081 − 2019). For compressive strength testing, 100mm×100mm×100mm cubic specimens shall be used; for splitting-tensile strength testing, 100mm×100mm×100mm cubic specimens shall be employed; and for flexural strength testing, 100mm×100mm×400mm prism specimens shall be utilized. Three parallel specimens shall be prepared for each group. After molding, specimens shall be cured in a standard curing chamber (20 ± 2℃, relative humidity ≥ 95%) for 3d,7d, and 28d ages, and mechanical property tests shall be conducted using the YES-2000 pressure testing machine. The loading rates for compressive strength testing shall be 0.5 ~ 0.8MPa/s, splitting-tensile strength testing shall be 0.02 ~ 0.05MPa/s, and flexural strength testing shall be 0.05 ~ 0.08MPa/s.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eMicro performance testing\u003c/h2\u003e \u003cp\u003e(1) Scanning Electron Microscopy (SEM) Analysis: Concrete specimens aged 28 days were selected. Samples measuring 5mm×5mm×5mm were cut near the aggregate-mortar interface transition zone (ITZ). After dehydration through anhydrous ethanol immersion, the specimens were polished sequentially with 400#,800#,1200#, and 2000# sandpaper, followed by gold sputtering. Microstructural morphology and ITZ structure were observed using a ZEISS Sigma 300 SEM at 15kV acceleration voltage. (2) X-ray Diffraction (XRD) Analysis: Cement paste specimens aged 28 days were crushed and ground to particle sizes below 80µm. After drying at 105°C until constant weight, phase analysis was performed using a Bruker D8 Advance XRD instrument. Test conditions: Cu Kα target, 40kV tube voltage, 40mA tube current, scanning range 5°~60°, scanning rate 5°/min. (3) Mercury Porosimetry (MIP) Analysis: Concrete core specimens aged 28 days were prepared as 5mm diameter × 5mm height cylindrical specimens. After vacuum drying, pore structure was measured using an AutoPore IV 9500 mercury porometer. The test pressure range was 0.006 ~ 414MPa, with measurable pore sizes ranging from 3.7nm to 100µm.\u003c/p\u003e \u003c/div\u003e "},{"header":"Experimental results and analysis","content":"\u003ch2\u003eSingle factor test results and analysis\u003c/h2\u003e\u003ch2\u003eInfluence of NC content on RAC rheological and mechanical properties\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the influence of NC content on RAC's rheological properties. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a), when NC content increases from 0% to 1.5%, the yield stress of RAC decreases from 87.6Pa to 60.8Pa, representing a 30.6% reduction. However, beyond 1.5%, the yield stress begins to rise, reaching 79.2Pa at 2.5% content. This phenomenon occurs because low-content NC particles disperse uniformly, effectively filling micro-pores in the cement paste and reducing inter-particle friction, thereby lowering the yield stress. Conversely, high-content NC particles exhibit higher surface energy, leading to agglomeration that increases internal friction resistance within the paste, ultimately elevating the yield stress.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b), the variation trend of plastic viscosity aligns with the yield stress: When the NC content ranges from 0% to 1.5%, the plastic viscosity decreases from 32.4Pa·s to 24.1Pa·s, representing a 25.6% reduction. However, when the content exceeds 1.5%, the plastic viscosity increases with further addition. This phenomenon occurs because NC particles act as \"ball bearings\" between cement particles, reducing the flow resistance of the paste. Conversely, the formation of agglomerates disrupts this \"ball bearing effect\" while simultaneously increasing the paste's viscosity.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates the influence of NC content on the mechanical properties of RAC. As shown in the figure, the compressive strength at 3d,7d, and 28d all initially increased and then decreased with rising NC content, reaching peak values at 1.5% NC content. Specifically, the 28-day compressive strength increased from 42.4MPa in the control group to 53.7MPa, representing a 26.7% improvement. The 3d and 7d compressive strengths showed increases of 29.8% and 27.3%, respectively. The trends for splitting tensile strength and flexural strength mirrored those of compressive strength: At 1.5% NC content, the 28-day splitting tensile strength reached 3.8MPa (26.7% increase), while the flexural strength achieved 6.5MPa (22.6% increase).\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eThe enhanced mechanical strength of low-NC-cement mixtures primarily stems from two mechanisms: First, the nucleation effect of NC accelerates cement hydration, generating more C-S-H gel and refining the microstructure. Second, the filling effect reduces internal porosity and improves density. When NC content exceeds 1.5%, agglomerates form internal defects that induce stress concentration under external forces, leading to strength reduction! Based on rheological and mechanical performance evaluations, the optimal NC!! content range is 1.0%–1.5%.\u003c/p\u003e\u003ch2\u003eEffect of regenerated aggregate replacement rate on rheological and mechanical properties of RAC\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the impact of recycled aggregate replacement rates on the rheological properties of RAC. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, when the recycled aggregate replacement rate increases from 0% to 100%, the yield stress rises from 65.2Pa to 112.8Pa, representing a 73.0% increase, while plastic viscosity rises from 25.8Pa·s to 41.2Pa·s, showing a 59.7% improvement. This is attributed to the rough surface and sharp edges of recycled aggregates, which adhere to hardened cement mortar and increase frictional resistance between aggregates and the paste. Additionally, the high water absorption capacity of recycled aggregates draws free water from the paste, leading to increased viscosity and degraded flowability. When the replacement rate is below 50%, the deterioration in rheological properties occurs gradually. However, when exceeding 50%, the deterioration accelerates significantly, primarily due to the cumulative effect of defects in recycled aggregates becoming more pronounced.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e illustrates the impact of recycled aggregate replacement rates on the mechanical properties of RAC. The results demonstrate a consistent decline in mechanical strength as the replacement rate increases: From 0% to 100%, the 28-day compressive strength drops from 50.2MPa to 35.6MPa (29.1% decrease), tensile strength decreases from 3.9MPa to 2.6MPa (33.3% reduction), and flexural strength declines from 6.8MPa to 4.7MPa (30.9% decrease). The primary reasons for this strength reduction include: ① Recycled aggregates exhibit lower inherent strength than natural aggregates, with crushing index values 1.8 times lower (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), resulting in reduced load-bearing capacity; ② A weak interfacial transition zone (ITZ) forms between recycled aggregate surface cement mortar and fresh mortar, prone to microcracking; ③ The high porosity of recycled aggregates reduces concrete density. When the replacement rate reaches 50%, the 28-day compressive strength still achieves 43.8MPa, meeting C40 concrete requirements. Given the high utilization rate of recycled aggregates, a 50% replacement rate proves optimal for balancing performance and cost-effectiveness.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003ch2\u003eInfluence of water-to-cement ratio on RAC rheological and mechanical properties\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrates the influence of water-to-cement ratio on RAC's rheological properties. As shown in the figure, when the water-to-cement ratio increases from 0.35 to 0.45, the yield stress decreases from 98.5Pa to 52.3Pa, representing a 46.9% reduction, while plastic viscosity drops from 38.6Pa·s to 21.4Pa·s, showing a 44.6% decrease. This improvement is attributed to the increased free water content in the paste, enhanced cement particle dispersion, reduced inter-particle cohesion, and decreased flow resistance, which collectively lead to significant enhancements in rheological performance. However, when the water-to-cement ratio exceeds 0.45, fresh concrete becomes prone to segregation and water bleeding, compromising construction quality. Conversely, a ratio below 0.35 results in excessively viscous paste, making concrete placement more challenging.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e illustrates the influence of water-to-cement ratio on RAC mechanical properties. As shown in the figure, mechanical strength demonstrates a significant decline with increasing water-to-cement ratio: When the ratio rises from 0.35 to 0.45, the 28-day compressive strength decreases from 56.3MPa to 39.8MPa, representing a 29.3% reduction; the splitting tensile strength drops from 4.2MPa to 3.0MPa (28.6% decrease); and the flexural strength diminishes from 7.1MPa to 5.2MPa (26.8% reduction). This phenomenon occurs because higher water-to-cement ratios reduce the density of cement hydration products, increase internal porosity, and allow residual moisture to evaporate, leaving more voids that form stress concentration sources. Comprehensive rheological and mechanical analysis indicates that at a water-to-cement ratio of 0.40, RAC achieves optimal performance with a yield stress of 72.5Pa and plastic viscosity of 28.3Pa·s, meeting construction workability requirements while attaining a 28-day compressive strength of 48.6MPa.\u003c/p\u003e\u003ch2\u003eOrthogonal test results and optimization analysis\u003c/h2\u003e\u003ch2\u003eOrthogonal test results\u003c/h2\u003e\u003cp\u003eThe rheological and mechanical property test results of the orthogonal experiment are presented in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Using yield stress (lower is better), plastic viscosity (lower is better), and 28-day compressive strength (higher is better) as evaluation indicators, the mix design was optimized through a comprehensive scoring method. The scoring calculation method involves standardizing each indicator's test value to a 0-100 point scale: yield stress and plastic viscosity undergo reverse standardization (lower values receive higher scores), while compressive strength adopts forward standardization (higher values receive higher scores). Based on engineering requirements, the weights assigned to yield stress, plastic viscosity, and compressive strength are 0.3, 0.2, and 0.5, respectively. The comprehensive score is calculated as: (yield stress score × 0.3) + (plastic viscosity score × 0.2) + (compressive strength score × 0.5).\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\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\u003eL₉(3⁴) orthogonal experiment test results and comprehensive score.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTest number\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNC content/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReclaimed aggregate replacement rate/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWater-to-gel ratio\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eYield stress /Pa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eViscosity (Pa·s)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28d compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eOverall score\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e78.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e29.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e50.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e82.5\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e72.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e27.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e49.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e84.2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e89.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e33.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e45.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e73.1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e65.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e24.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e52.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e89.6\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e75.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e28.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e50.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e83.8\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e82.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e30.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e48.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e79.3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e79.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e31.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e49.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e80.1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.38\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e73.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e28.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e51.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e85.4\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e70\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e92.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e34.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e44.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e71.5\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003ch2\u003eRange and variance analysis\u003c/h2\u003e\u003cp\u003eTo assess the significance of each factor's impact on evaluation indicators, range analysis and ANOVA were performed on the orthogonal test results (Tables\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). In range analysis, a larger R value indicates a more significant factor effect. For ANOVA, higher F values and lower P values demonstrate greater significance (P \u0026lt; 0.05 indicates significant effect, P \u0026lt; 0.01 indicates highly significant effect).\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\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\u003eThe range analysis results of the influence of various factors on different evaluation indicators.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEvaluating indicator\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003efactor\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eHorizontal 1 Mean\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHorizontal 2 Mean\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHorizontal 3 Mean\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eRange R\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eImpact order\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eYield stress /Pa\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (NC content)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e80.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e74.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e81.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e7.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eB \u0026gt; C \u0026gt; A\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (Replacement rate)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e74.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e73.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e88.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14.3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC (water-to-cement ratio)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e77.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e80.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eViscosity (Pa·s)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (NC content)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e31.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eB \u0026gt; A \u0026gt; C\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (Replacement rate)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e28.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e34.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e7.3\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC (water-to-cement ratio)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e29.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e30.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e28d compressive strength/MPa\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (NC content)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e50.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eB \u0026gt; A \u0026gt; C\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (Replacement rate)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e50.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e46.0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e4.7\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC (water-to-cement ratio)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e49.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e48.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eOverall score\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eA (NC content)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e79.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e84.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e78.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e5.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eB \u0026gt; A \u0026gt; C\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (Replacement rate)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e84.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e84.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e74.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9.9\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC (water-to-cement ratio)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e82.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e81.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e78.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"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\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe results of the variance analysis of the comprehensive score.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSource of variation\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSum of Squares\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003efree degree\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003emean square\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eF price\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP price\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003econspicuousness\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA (NC content)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e48.62\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24.31\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15.23\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.028\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003enotable\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB (Replacement rate)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e126.35\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e63.18\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.65\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHighly significant\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC (water-to-cement ratio)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.58\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.79\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.77\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.083\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003equiet\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eError\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.19\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.60\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSum\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e199.74\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs shown in Tables\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e: ① The replacement rate of recycled aggregates (B) significantly affects the composite score (P = 0.005), being the primary factor influencing RAC performance; ② NC content (A) shows significant influence (P = 0.028), ranking as a secondary factor; ③ Water-to-binder ratio (C) demonstrates no significant effect (P = 0.083). Based on the average levels of all factors, the optimal mix design is A₂B₂C₂, comprising 1.2% NC content, 50% recycled aggregates, and a water-to-binder ratio of 0.40.\u003c/p\u003e\u003ch3\u003eOptimal mix ratio verification test\u003c/h3\u003e\u003cp\u003eTo validate the reliability of the optimal mix design, three test specimens were prepared: (1) an optimal mix specimen (A₂B₂C₂: 1.2% NC content, 50% recycled aggregate replacement, water-to-binder ratio 0.40), (2) a control specimen (0% NC content, 0% recycled aggregate replacement), and (3) an orthogonal test specimen from Group 4 (A₂B₁C₂: 1.2% NC content, 30% recycled aggregate replacement, water-to-binder ratio 0.40). Their rheological and mechanical properties were compared, with the results presented in Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\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\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab9\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe verification results of rheological and mechanical properties of the optimal mix ratio and the control group.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNC content/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReclaimed aggregate replacement rate/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eWater-to-gel ratio\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eyield stress /Pa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eViscosity (Pa·s)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3d compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7d compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e28d compressive strength/MPa\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBaseline group\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e76.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e29.7\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e32.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e41.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e49.6\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOrthogonal Group 4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e65.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e24.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e35.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e45.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e52.1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBest mix ratio group\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e68.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e25.9\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e34.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e44.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e52.8\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e: ① Although the yield stress (68.4Pa) and plastic viscosity (25.9Pa·s) of the optimal mix design slightly exceed those of Orthogonal Group 4, they are significantly lower than the reference group (reduced by 10.9% and 12.8% respectively), meeting the pumping construction requirements for fresh concrete rheological properties (yield stress 50–80 Pa, plastic viscosity 20–30 Pa·s); ② In terms of mechanical properties, the optimal mix achieved a 28-day compressive strength of 52.8MPa, representing a 6.5% improvement over the reference group and a 1.3% increase compared to Orthogonal Group 4. The 3-day and 7-day compressive strengths also outperformed the reference group, with improvements ranging from 6.5% to 7.3%; ③ Compared to Orthogonal Group 4 with a 30% recycled aggregate replacement rate, the optimal mix increased recycled aggregate utilization to 50%, significantly enhancing solid waste resource efficiency while maintaining performance, aligning with green building development needs. Verification results demonstrate that the optimal mix achieves excellent rheological properties, mechanical performance, and cost-effectiveness, confirming the reliability of the optimization outcomes.\u003c/p\u003e\u003ch2\u003eMicro performance analysis\u003c/h2\u003e\u003cp\u003eTo investigate the modification mechanism of NC on RAC, three groups were selected for SEM, XRD, and MIP analysis: the control group, the optimal mix ratio group, and the recycled aggregate concrete group without NC (RA50 group: 50% recycled aggregate replacement, 0% NC addition, water-to-binder ratio 0.40). The study aimed to analyze the changes in microstructure, phase composition, and pore structure.\u003c/p\u003e\u003ch2\u003eSEM microstructure analysis\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e presents SEM images of three concrete groups at 28-day age. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a) of the reference group, the interface transition zone (ITZ) between natural aggregates and cement paste exhibits a dense structure with minimal micro-pores, while the C-S-H gel displays fibrous interwoven distribution – this microstructural foundation explains the superior mechanical properties of the reference group. In contrast, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b) of the RA50 group reveals significant ITZ cracks and voids (2–5µm wide), with the C-S-H gel appearing as loose flocculent aggregates. The poor bond between recycled aggregates and newly applied mortar creates a \"double interface\" defect, which aligns with the macroscopic observation of its 28-day compressive strength being only 42.4MPa (14.5% lower than the reference group).\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(c) demonstrates significant improvements in the microstructure of the optimal mix design: ① ITZ region cracks have virtually disappeared, with their width reduced to below 0.5µm, and aggregates are tightly bonded with the cement paste; ② The C-S-H gel forms a dense network structure that fills the pores; ③ NC particles are uniformly dispersed in the paste without noticeable agglomeration, with some NC particles serving as nuclei encapsulated by the C-S-H gel. This is attributed to the dual effects of NC's interface modification enhancing ITZ's bonding strength and its nucleation effect promoting C-S-H gel formation. These combined mechanisms reduce microstructural defects and improve macroscopic mechanical properties.\u003c/p\u003e\u003ch2\u003eXRD phase composition analysis\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e presents XRD patterns of three concrete cement paste groups. All three spectra exhibit characteristic diffraction peaks of Ca(OH)₂, C₃S, C₂S, and calcite (CaCO₃), with the calcite peak primarily originating from carbonation of NC and cement hydration products. Compared to the reference group and RA50 group, the optimal mix ratio group shows a significant 23.8% reduction in the intensity of CH's characteristic diffraction peaks (2θ = 18.0°,34.1°), while the intensity of C-S-H gel's characteristic diffuse peaks (2θ = 20°~30°) markedly increases. CH, a product of cement hydration, can cause internal alkalinity imbalance in concrete when present in excess. Its plate-like crystalline structure tends to align directionally in ITZ regions, forming weak points. The reduced CH content in the optimal mix ratio group results from NC particles acting as nuclei that promote C₃S and C₂S hydration to generate more C-S-H gel, while simultaneously consuming part of CH and reducing its enrichment in ITZ. XRD results confirm NC's nucleation effect, demonstrating that optimizing the composition of hydration products enhances concrete's microstructure.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003ch2\u003eMIP pore structure analysis\u003c/h2\u003e\u003cp\u003eConcrete's macroscopic properties are closely related to its pore structure. Lower porosity and a higher proportion of non-hazardous pores (with pore size \u0026lt; 20nm) result in superior mechanical properties and durability. Table\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e presents the MIP test results for three concrete groups, while Fig.\u0026nbsp;10 shows the pore size distribution curve.\u003c/p\u003e\u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab10\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 10\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of concrete pore structure parameters in each group (MIP method).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal porosity/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNon-hazardous holes (\u0026lt; 20nm) ratio/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMinor pores (20–50 nm) proportion/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHarmful pores (50 ~ 200nm) ratio/%\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePorous material (\u0026gt; 200nm) proportion/%\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBaseline group\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e35.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28.6\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e13.8\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRA50 Group\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e18.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e30.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e22.1\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBest mix ratio\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e41.5\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e30.2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e18.8\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9.5\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs shown in Table\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e: ① The RA50 group achieved a total porosity of 18.5%, representing a 44.5% increase compared to the reference group, with harmful and multi-harmful pores accounting for 52.6% – the primary cause of its mechanical deterioration; ② The optimal mix proportion group reduced total porosity to 13.2%, slightly higher than the reference group but 28.6% lower than RA50; ③ The optimal mix proportion group increased harmless pore proportion to 41.5% while decreasing multi-harmful pores to 9.5%, demonstrating significant pore size distribution optimization. These results validate NC's filling effect: NC particles (30-80nm) effectively fill capillary pores (50-200nm) in cement paste, refine pore sizes, convert some harmful pores into harmless ones, and reduce water and harmful substance penetration pathways, thereby enhancing concrete density and mechanical strength.\u003c/p\u003e\u003ch3\u003eModification mechanism analysis\u003c/h3\u003e\u003cp\u003eBy integrating macroscopic performance with microscopic test results, NC's modification effect on RAC is achieved through three synergistic mechanisms: filling effect, nucleation effect, and interface modification. (1) Filling Effect: With particle sizes of 30–80 nm, NC particles effectively fill micro-pores in cement paste, voids on recycled aggregate surfaces, and ITZ regions. This reduces macroscopic defects, refines pore size distribution, lowers total porosity (Table\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e), and enhances concrete density. The filling effect directly improves both fresh concrete's rheological properties (reducing particle friction) and hardened concrete's mechanical performance (minimizing stress concentration). (2) Nucleation Effect: NC's surface contains abundant active sites that adsorb Ca²⁺ and SiO₄⁴⁻ ions from cement hydration. These ions act as nucleation sites for C-S-H gel formation, promoting C₃S and C₂S hydration (as evidenced by reduced CH content and increased C-S-H gel in XRD analysis). The resulting C-S-H gel forms a network-like structure that strengthens inter-particle bonding while filling pores, optimizing the microstructure. (3) Interface Modification: The \"dual interface\" of recycled aggregates remains a weak point in RAC. NC enhances interface performance through two pathways: ① Adsorption of NC particles on aggregate surfaces improves physical bonding between paste and aggregate; ② NC promotes C-S-H gel formation in ITZ regions, reducing CH crystal orientation and eliminating interface cracks (SEM image 8), thereby transforming ITZ from a \"weak zone\" to a \"strengthened zone\". Three synergistic effects work in tandem: The filling effect creates a dense reaction environment for nucleation, while the hydration products generated by nucleation enhance the filling effect. Interface modification improves the structural load-bearing capacity, ultimately achieving synergistic optimization of RAC's rheological and mechanical properties.\u003c/p\u003e"},{"header":"Conclusions and outlook","content":"\u003cp\u003eThe effects of NC dosage, recycled aggregate substitution rate, and water-to-cement ratio on RAC performance are significant and follow clear patterns: ① Performance peaks at NC dosage of 1.0%~1.5%, while excessive dosage causes performance degradation due to agglomeration; ② Recycled aggregate substitution rate shows negative correlation with RAC performance, with 50% being the optimal balance point for both performance and cost-effectiveness; ③ Rheological and mechanical properties achieve optimal synergy at water-to-cement ratio of 0.40. Orthogonal experiments optimized the best RAC mix design: NC dosage 1.2%, recycled aggregate substitution rate 50%, water-to-cement ratio 0.40. Under this mix design, RAC exhibits yield stress 68.4Pa and plastic viscosity 25.9Pa\u0026middot;s, meeting construction requirements; 28-day compressive strength reaches 52.8MPa, 6.5% higher than the reference group and 24.5% higher than the NC-free RA50 group. NC synergistically modifies RAC through three effects: pore-filling (refining pores), nucleation (promoting C-S-H gel formation), and interface modification (strengthening ITZ). The interface modification effect addresses the \"double interface\" defect, while nucleation and pore-filling further optimize microstructure to enhance macroscopic performance. This NC-modified RAC technology proposed in this study achieves 50% recycled aggregate utilization while maintaining C40 concrete performance, providing an economically viable solution for construction solid waste recycling. Aligning with \"dual carbon\" goals and green building concepts, it can be widely applied in municipal engineering and residential building load-bearing structures. Future research could focus on the following directions: ① Investigate the synergistic effects of NC with other modifiers to further enhance RAC performance; ② Conduct long-term durability tests to clarify the performance evolution patterns of NC-modified RAC under harsh conditions such as freeze-thaw cycles and chloride salt erosion; ③ Explore the hydration heat release patterns and volume deformation characteristics of NC-modified RAC to provide a basis for large-volume concrete construction.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003eThis research was funded by the financial support from the Science and technology project of Zhejiang Huadong Geotechnical Investigation \u0026amp; Design Institute CO, Ltd (KY2019-XNY-03-06, KY2021-XNY-03-02, KY2024-XNY-03-01).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData curation, Xu Jun; Funding acquisition and Investigation, Lyu Guang-hua; \u0026nbsp; Methodology and Project administration, Tan Min; Resources,Tan Min; Supervision, Lyu Guang-hua; Writing\u0026mdash;original draft, Xu Jun; Writing\u0026mdash;review \u0026amp; editing, Xu Jun. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author(s) declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFeng, C., Cui, B., Ge, H., Huang, Y. \u0026amp; Zhang, W. Reinforcement of recycled aggregate by microbial-induced mineralization and deposition of calcium carbonate\u0026mdash;influencing factors, mechanism and effect of reinforcement. \u003cem\u003eCrystals\u003c/em\u003e \u003cb\u003e11\u003c/b\u003e, 887. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/cryst11080887\u003c/span\u003e\u003cspan address=\"10.3390/cryst11080887\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiao, J., Deng, Q., Duan, Z., Hou, S. \u0026amp; Tao, J. Carbonization modification of recycled fine aggregates and its influence on the rheological properties of mortar. \u003cem\u003eJ. Appl. Basic. Sci. Eng.\u003c/em\u003e \u003cb\u003e32\u003c/b\u003e, 1486\u0026ndash;1495. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.16058/j.issn.1005-0930.2024.05.021\u003c/span\u003e\u003cspan address=\"10.16058/j.issn.1005-0930.2024.05.021\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2024).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDan, Y., Liang, Y., Xu, R., Ning, F. \u0026amp; Chen, Z. Experimental study on the early mechanical properties of recycled aggregate concrete after carbonation of NaHCO₃. \u003cem\u003eJ. Compos. Mater.\u003c/em\u003e \u003cb\u003e42\u003c/b\u003e, 3371\u0026ndash;3383. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.13801/j.cnki.fhclxb.20240903.006\u003c/span\u003e\u003cspan address=\"10.13801/j.cnki.fhclxb.20240903.006\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, M., Ding, Y., Yang, X. \u0026amp; Sun, B. Mechanical properties and strengthening mechanism of nano-SiO₂ composite carbonized fully recycled aggregate concrete. \u003cem\u003eJ. Compos. Mater.\u003c/em\u003e \u003cb\u003e42\u003c/b\u003e, 2102\u0026ndash;2111. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.13801/j.cnki.fhclxb.20240522.007\u003c/span\u003e\u003cspan address=\"10.13801/j.cnki.fhclxb.20240522.007\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen, Z., Zhang, Y., Chen, J. \u0026amp; Fan, J. Sensitivity factors analysis on the compressive strength and flexural strength of recycled aggregate infill wall materials. \u003cem\u003eAppl. Sci.\u003c/em\u003e \u003cb\u003e8\u003c/b\u003e, 1090. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/app8071090\u003c/span\u003e\u003cspan address=\"10.3390/app8071090\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, G. et al. Acoustic emission characteristics and damage mechanisms investigation of basalt fiber concrete with recycled aggregate. \u003cem\u003eMaterials\u003c/em\u003e \u003cb\u003e13\u003c/b\u003e, 4009\u0026ndash;4031. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ma13184009\u003c/span\u003e\u003cspan address=\"10.3390/ma13184009\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, J., Zhou, Z. \u0026amp; Cheng, X. Formation kinetics of regenerated cement clinker calcined by using wasted recycling concrete powders as raw meals. \u003cem\u003eAdv. Mater. Res.\u003c/em\u003e \u003cb\u003e1073\u0026ndash;1076\u003c/b\u003e, 1309\u0026ndash;1312. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.4028/www.scientific.net/amr.1073-1076.1309\u003c/span\u003e\u003cspan address=\"10.4028/www.scientific.net/amr.1073-1076.1309\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZheng, L. \u0026amp; Pang, J. Basic mechanical properties of recycled concrete aggregate the impact study. \u003cem\u003eJ. Shanxi Norm Univ.\u003c/em\u003e \u003cb\u003e39\u003c/b\u003e, 78\u0026ndash;82. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.16207/j.cnki.1009-4490.2025.03.004\u003c/span\u003e\u003cspan address=\"10.16207/j.cnki.1009-4490.2025.03.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhong, C. et al. Recycled fine aggregate mortar of carbide and the influence of mechanical properties of concrete. \u003cem\u003eJ. Silic Bull.\u003c/em\u003e \u003cb\u003e44\u003c/b\u003e, 1468\u0026ndash;1476. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.16552/j.cnki.issn1001-1625.2024.1402\u003c/span\u003e\u003cspan address=\"10.16552/j.cnki.issn1001-1625.2024.1402\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, X., Jiang, X., Liu, Y. \u0026amp; Deng, H. Orthogonal experiment and numerical simulation of influencing factors on compressive strength of recycled aggregate concrete. \u003cem\u003eHydro Energy Sci.\u003c/em\u003e \u003cb\u003e43\u003c/b\u003e, 93\u0026ndash;98. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.20040/j.cnki.1000-7709.2025.20240333\u003c/span\u003e\u003cspan address=\"10.20040/j.cnki.1000-7709.2025.20240333\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (2025).\u003c/span\u003e\u003c/li\u003e\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":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"nano CaCO₃, recycled aggregate concrete, rheological properties, mechanical properties, interfacial transition zone, optimization","lastPublishedDoi":"10.21203/rs.3.rs-8439637/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8439637/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTo address poor rheological properties and low mechanical strength of recycled aggregate concrete (RAC) caused by recycled aggregate (RA) defects, this study investigated effects of nano-CaCO₃ (NC) on RAC's rheological (yield stress, plastic viscosity) and mechanical (compressive, splitting, flexural strength) properties under varying NC content (0%\u0026ndash;2.5%), recycled aggregate replacement rates (0%\u0026ndash;100%), and water-to-binder ratios (0.35\u0026ndash;0.45). Orthogonal experiments optimized mix design, and SEM, XRD, MIP elucidated modification mechanisms. Results showed 1.0%\u0026ndash;1.5% NC reduced yield stress by 23.6%\u0026ndash;31.2% and plastic viscosity by 18.9%\u0026ndash;25.3%, while increasing 28-day compressive strength by 20.3%\u0026ndash;26.7%. Optimal mix (1.2% NC, 50% recycled aggregate replacement, 0.40 water-to-binder ratio) yielded RAC with construction-appropriate rheological properties and 28-day compressive strength of 52.8MPa (24.5% higher than reference). NC enhanced performance via pore refinement (filling effect), promoted hydration (nucleation effect), and improved aggregate-mortar interface (ITZ modification). This study provides theoretical and technical support for NC application in RAC engineering.\u003c/p\u003e","manuscriptTitle":"Study on rheological and mechanical properties optimization and mechanism of Nano-CaCO₃ regenerated aggregate concrete","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-05 09:37:45","doi":"10.21203/rs.3.rs-8439637/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-16T16:02:31+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-15T06:08:23+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-14T20:35:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"225022757487180490968507613368626058573","date":"2026-01-04T06:23:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"160595092944526426012307239557533256876","date":"2026-01-03T15:08:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"116825000898676148556636774677324557164","date":"2026-01-02T15:41:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"160081627733328932451884880117633486885","date":"2026-01-02T12:37:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"136352123474509775749949437945067354154","date":"2026-01-02T12:29:35+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-02T12:08:11+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-01-02T10:24:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-29T08:57:56+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-29T08:56:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-12-24T06:20:41+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"dc388a9a-c70a-4652-b268-2d69135d7306","owner":[],"postedDate":"January 5th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":60543264,"name":"Physical sciences/Engineering"},{"id":60543265,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2026-04-27T16:03:45+00:00","versionOfRecord":{"articleIdentity":"rs-8439637","link":"https://doi.org/10.1038/s41598-026-49784-6","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-04-20 15:57:39","publishedOnDateReadable":"April 20th, 2026"},"versionCreatedAt":"2026-01-05 09:37:45","video":"","vorDoi":"10.1038/s41598-026-49784-6","vorDoiUrl":"https://doi.org/10.1038/s41598-026-49784-6","workflowStages":[]},"version":"v1","identity":"rs-8439637","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8439637","identity":"rs-8439637","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}