Effect of Interface Transition Zone on Compressive Properties of Recycled Aggregate Concrete

With the increasing amount of construction waste and the depletion of natural resources, recycled aggregate concrete (RAC) has attracted wide attention as a sustainable building material. However, the complex structural characteristics of the interface transition zone (ITZ) in RAC significantly impact its mechanical properties. Through the combination of mesoscopic structural modeling and test verification, this study systematically explored the influence of different replacement ratios of recycled coarse aggregate (RCA), ITZ thickness (0.5–1.5 mm), and ITZ strength (10–21 MPa) on the axial compressive properties of RAC. The results showed that for every 0.5 mm increase in ITZ thickness, the elastic modulus of RAC decreased by 4.25% to 20.49%, and the peak strain increased by 6.9% to 22.22%. The increase in ITZ strength increased the peak stress by 3.76% to 26.64% and enhanced the energy dissipation capacity by 1.27% to 7.01%. By analyzing the failure process of ITZ, the micromechanical mechanism of RAC under compression was revealed. Based on numerical simulation results, this study developed a predictive model for the axial compressive strength of RAC that accounts for the multiparameter coupling of the replacement ratio of RCA, ITZ thickness, and ITZ strength. The model effectively quantifies the influence of mesoscopic parameters on the macroscopic mechanical properties of RAC, thereby providing a reliable tool for optimizing the mix design of RAC and having important engineering value in promoting the application of green and low-carbon building materials.