Study on Road Performance and Substitution Rate Optimization of Highway Solid Waste Recycled Aggregate

In view of the differences in the specified substitution rates of construction and demolition waste (C&DW) recycled materials in road applications between China and other countries, this study focuses on a highway reconstruction and expansion project in Guangdong Province, China, and systematically analyzes the influence of the recycled aggregate substitution rate on the road performance of subgrade filler and cement-stabilized recycled aggregate (CSRA). Based on the current domestic JTG series specifications, combined with a literature review and comparative analysis, the effects of particle size, maximum dry density (MDD), optimum moisture content (OMC), and California bearing ratio (CBR) on the compactness, stability, and strength of subgrade fillers under different substitution rates were systematically evaluated. Furthermore, the study investigates the variation in the performance of CSRA, including crushing value, 7-day unconfined compressive strength, 90-day splitting tensile strength, compressive rebound modulus, and scouring resistance. The results indicate that (1) when recycled materials are used for roadbed filling, they can meet the specified compactness and CBR value requirements at a 100% substitution rate. The key is to control the impurity content and maximum particle size during the crushing process. (2) When recycled materials are used in a pavement structure layer, their performance is significantly affected by the material source and substitution rate. CSRA produced from demolished old pavements and bridges exhibits better performance. It is recommended that the substitution rate should not exceed 80% for subbase layers and 50% for base layers. This research provides recommended substitution rates and material-selection guidelines for the scientific utilization of C&DW recycled materials for specific engineering applications. The study has practical significance for improving C&DW resource utilization, reducing engineering costs, and lowering carbon emissions.