Epoxy resin-modified concrete (ERMC) demonstrates significant potential for enhancing the durability of concrete structures exposed to harsh environmental conditions. However, the performance of ERMC under the combined effects of salt erosion and freeze–thaw cycles remains inadequately explored. This study systematically evaluates the durability of ERMC through experimental investigations on specimens with epoxy resin-poly ash ratios of 0%, 5%, 10%, 15%, 20%, and 25%. Resistance to salt erosion was assessed using composite salt solutions with concentrations of 0%, 1.99%, 9.95%, and 19.90%, while frost resistance was tested under combined conditions using a 1.99% Na₂SO₄ solution. Key performance metrics were analyzed with microstructural observations to elucidate the underlying damage mechanisms, including the compressive strength corrosion coefficient, dynamic elastic modulus, mass loss rate, and flexural strength loss rate. The results reveal that incorporating epoxy resin enhances concrete’s resistance to salt erosion and freeze–thaw damage by inhibiting crack propagation and reducing pore development. Optimal performance was achieved with an epoxy resin content of 10–15%, which exhibited minimal surface deterioration, a denser microstructure, and superior long-term durability. These findings provide critical insights for optimizing the design of ERMC to improve the resilience of concrete structures in aggressive environments, demonstrating that ERM is a sustainable material, and offering practical implications for infrastructure exposed to extreme climatic and chemical conditions.

To promote the high-value utilization of construction and demolition waste in cementitious materials, this study proposed an integrated strengthening strategy combining recycled coarse aggregate modification with cementitious matrix optimization. Recycled coarse aggregates with particle sizes of 4.75–31.5 mm were prepared from demolished concrete waste collected in Aksu, Xinjiang, China, and treated by particle shaping, alkaline solutions, and polyvinyl alcohol (PVA). Silica fume and a polycarboxylate superplasticizer were used to optimize the cementitious matrix. The physical properties of recycled aggregates, the mechanical performance of recycled aggregate concrete, and the mechanical and durability performance of high-content recycled aggregate cement-stabilized materials were evaluated. Particle shaping reduced water absorption and the crushing index from 6.8% and 14.4% to 5.6% and 12.6%, respectively. After treatment with 5% NaOH and 10% PVA, the apparent density increased to 2779 kg/m³, whereas water absorption and the crushing index decreased to 3.3% and 8.3%, meeting Class II recycled coarse aggregate requirements. With 10% silica fume and 0.2% superplasticizer, the 28-day compressive strength of recycled aggregate concrete prepared with the optimized aggregate and matrix reached 27.6 MPa, corresponding to 97.5% of that of natural aggregate concrete. The combined modification approach improved mechanical performance and reduced drying shrinkage, but the replacement ratio should be limited to 60% to satisfy the F50 freeze–thaw requirement under the tested conditions.

Ecological concrete designed by empirical method does not consider the mesoscopic influence of aggregates, resulting in problems such as low strength, excessive porosity, and poor stability with different gradations, which severely restricts the development and application of ecological concrete. To achieve the refined design of ecological concrete, a mesoscopic specific surface area design method based on statistical analysis is proposed. First, the meso-aggregate model with sub-millimeter precision was established using a high-precision 3D scanner, and CloudCompare was used to calculate the specific surface area of the mesoscopic aggregate model, laying the foundation for the statistical analysis of specific surface area. Second, statistical analysis methods verified that the mean specific surface area of 20 aggregates from a single random sampling reliably estimates the mean of the overall aggregate population. Third, the optimal water–cement ratio was calculated considering the water absorption characteristics and the mortar-wrapping capacity of aggregates; standard cubic specimens were prepared using this optimal water–cement ratio, with aggregates evenly coated with mortar and no obvious mortar settlement. Fourth, the cubic compressive strength of specimens naturally cured for 7 days was tested; experimental results showed that the cubic compressive strength of specimens formed by this project’s design method increased by more than 30% compared to the empirical design method. The results indicate that using the average volume-specific surface area of 20 aggregates to assess the overall average volume-specific surface area of aggregates is both reliable and relatively efficient. Based on the reliable estimation of the overall average volume-specific surface area of aggregates derived from this method, measurements were taken of the thickness of water films adsorbed on dry aggregates and the thickness of mortar coatings on surface-dry aggregates. Further, the optimal water–cement ratio for eco-concrete was deduced, and a comprehensive set of feasible refined methods for eco-concrete mix proportion design was proposed. In contrast to the empirical method, concrete designed via the subject’s methodology exhibits a marked enhancement in compressive strength while retaining favorable pore characteristics—rendering it well-suited for deployment in the slope protection of reservoirs and ponds and thereby facilitating the realization of ecological slope protection functionality.

To improve the durability of concrete in the saline environment of southern Xinjiang, concrete was modified with basalt fiber (BF) and waterborne epoxy (WEP). A one-year outdoor natural-exposure test in Aksu, Xinjiang, systematically investigated the corrosion resistance and multi-scale deterioration behavior and durability of the modified concrete. Compared with C0, the BF2E2 mixture reduced the mass loss rate and flexural strength loss rate by 54.65% and 37.20%, respectively, while increasing the relative dynamic elastic modulus by 14.55%. The modified mixtures also showed decreased total porosity, reduced average pore area, and narrowed crack widths, with significantly attenuated diffraction peaks of corrosion products. Threshold-crossing times obtained by extrapolation indicated that the earliest threshold-crossing time of BF2E2 was extended by 62.14% compared with C0, with the relative dynamic elastic modulus serving as the governing durability criterion. Mechanistic analysis revealed that BF and WEP acted collaboratively through fiber bridging and polymer filling, forming a dual-reinforcement network that suppressed deterioration from the microstructural to the macroscopic scale. These findings provide guidance for the durability-oriented design of concrete structures in saline environments.