Influence of Saturation Degree of Recycled Coarse Aggregate on the Mechanical Properties of Fully Recycled Aggregate Concrete and Mechanism Analysis

The application of fully recycled aggregate concrete (FRAC) promotes sustainable construction, but its mechanical properties are often unstable due to the high absorption and variability of recycled aggregates. This study investigates the effect of saturation degrees of recycled coarse aggregate (RCA) and recycled fine aggregate (RFA) on FRAC’s mechanical performance and failure mechanisms. Results show that optimal strength is achieved at 70% RCA and 25% RFA saturation. Reducing RFA saturation from 100% to 25% increases compressive strength by 28.8% and tensile strength by 34.6%. RFA saturation has a greater influence than sand ratio or superplasticizer dosage, second only to water–cement ratio. Analysis indicates that excessive saturation leads to pores and microcracks in the interfacial transition zone, weakening bonding. A multiple linear regression model based on recycled aggregate saturation accurately predicts FRAC properties, supporting optimized use of recycled materials and cleaner construction practices.