The influence of four factors (water‐binder ratio, recycled coarse aggregate replacement rate, fly ash substitution rate, and superplasticizer content) on the workabilities and mechanical properties of recycled coarse aggregate self‐compacting concrete (RCASCC) was studied using the orthogonal test method. Based on the orthogonal test design and range analysis method of the fresh and hardened properties of RCASCC, the optimal mix is as follows: water‐binder ratio of 0.269, recycled coarse aggregate replacement rate of 30%, fly ash substitution rate of 40%, and superplasticizer content of 0.50%. Then, the porosity and aperture size distribution of nine groups of RCASCC were tested by mercury intrusion porosimetry (MIP) at the microlevel. The macroscopic and microscopic relationship was established by combining the results of mechanical property tests and MIP. Fractal dimension D of the B.B. Mandelbrot model was used to study the fractal characteristics of pore volume of RCASCC. Results showed that porosity and strengths are negatively correlated, and the relative strength can be roughly judged according to the porosity. The pore structure of nine groups of RCASCC materials has evident fractal characteristics of irregular shape. The complex pore structure adversely affects strength.

To protect the environment and reduce the consumption of natural resources, this study investigated the performance of self-compacting concrete (SCC) utilizing aeolian sand (AS) as a replacement for fine aggregate and recycled coarse aggregate (RCA) as a replacement for natural coarse aggregate. Twelve mixing ratios were prepared, with AS replacement ratios at 0, 20%, 40%, and 60% and RCA replacement ratios at 0, 25%, and 50%. The evaluation primarily focused on workability, uniaxial compressive strength, split tensile strength, stress–strain curve, modulus of elasticity, and axial compressive strength. The results indicated that both AS and RCA can enhance the performance of SCC at appropriate replacement ratios, and a 20% AS and 50% RCA replacement ratio significantly improved the performance of SCC. In addition, the effects of AS and RCA replacements on SCC were evaluated by several performance indexes, which provides a basis for subsequent experimental studies and demonstrates the feasibility of incorporating AS and RCA into SCC.

Aeolian sand (AS) and recycled coarse aggregate (RCA) can be reasonably utilized as green materials for concrete modification. The paucity of natural sand and gravel in the construction industry is anticipated to be remedied by the use of these two eco-friendly concrete ingredients. This is incredibly important for environmental protection. Study on the damage law of self-compacting concrete with the addition of AS and RCA (ARSCC) under severely cold conditions is of great significance for the promotion and implementation of this material. In this study, 12 groups of ARSCC specimens were prepared for freeze–thaw cycle experiments, with AS substitution rates of 0, 20%, 40%, and 60% as well as RCA replacement rates of 0, 25%, and 50%. Then, the degradation mechanism of ARSCC freeze–thaw damage was discussed from both macroscopic and microscopic perspectives via mass loss rate (W_n), relative dynamic modulus of elasticity (P_n), bubble spacing factor, and SEM analysis. Finally, the response surface method was utilized to determine the damage variable. A freeze–thaw damage model for ARSCC was developed based on the Weibull distribution and Grey theories. The results showed that the P_n could reflect the evolution law of the internal structure of ARSCC. Appropriate addition of AS to fill the large, harmful pores in RCA would inhibit freeze–thaw damage of ARSCC. The optimum substitution rates of AS and RCA were determined to be 20–40% and 25–50%, respectively. In addition, the values obtained from theoretical damage modeling and experiments were in good agreement. The acquired damage model had the potential to predict ARSCC damage under freeze–thaw cycles.

Self-compacting concrete has seen extensive application in both engineering and construction. In order to save building resources, aeolian sand—recycled coarse aggregate self-compacting concrete (ARSCC) is created by partially substituting recycled coarse aggregates (RCA) and aeolian sand (AS) for natural coarse aggregates. For ten groups with different mechanical and durable properties, this study examined the effects of sulfate erosion, chloride penetration resistance, and related impermeability, as well as AS replacement ratios of 20%, 40%, and 60% and RCA replacement ratios of 25%, 50%, and 75% in ARSCC and a control group (A0-R0). According to the study’s findings, after sulfate attack, the highest relative dynamic elastic modulus and corrosion resistance factor were obtained with the 20% AS replacement ratio and 50% RCA replacement ratio (A20-R50). The highest impermeability grade and lowest electric flux were obtained with the 20% AS replacement ratio and 25% RCA replacement ratio (A20-R25). X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) revealed that the addition of aeolian sand and recycled coarse aggregates improved the pore structure of the SCC and increased the densification of the self-compacting concrete, particularly following sulfate attack. This study highlights the importance of recycled aggregates and aeolian sand in engineering applications and the sustainable growth of the concrete industry, both of which support resource conservation and environmental protection.

This study examined the impact of sulfate and sulfate–chloride dry–wet cyclic erosion on the mechanical properties and microscopic pore structure of engineered cementitious composite (ECC) with recycled fine aggregate (RA). Uniaxial tensile tests and four-point bending tests were conducted to evaluate the mechanical properties of RAECC, while the resonance frequency ratio was used to assess the integrity of the specimens. Finally, X-ray computed tomography (X-CT) reconstruction was employed to analyze the erosion effects on the microscopic pore structure. The results showed that the uniaxial tensile strength and flexural strength of the RAECC specimens in corrosive solution first increased and then decreased, and the 5% Na₂SO₄ solution caused the most serious erosion of the specimens. The resonance frequency ratio of the specimens reached the peak value when they were subjected to dry–wet cycles 15 times in the 5% Na₂SO₄ solution. During the erosion process, the pore space of the specimen first decreased and then increased, and the number of pores increased. The erosion process is the result of the erosion products continuously filling and eventually destroying the pores, and the erosion damage produces a large number of new pores and poor sphericity, leading to a decline in mechanical properties.