Damage-based ion transport in recycled aggregate concrete under external sulfate attack

Abstract

The utilization of recycled coarse aggregate (RCA) in replacement of natural coarse aggregate in the production of recycled aggregate concrete (RAC) may potentially lead to a reduction in the resistance of RAC to sulfate attack. In this study, the dynamic elastic modulus and sulfate ion transport of RAC was investigated by fully immersing RAC specimens produced with different water-to-cement ratios (W/C) and RCA volume fractions (VRCA) into sulfate (Na2SO4) solutions with different concentrations. The effects of W/C and VRCA on the initial damage velocity, damage acceleration, and service life of the RAC were analyzed by the defined damage evolution equations. The variation patterns of the ion diffusion coefficient and the surface ion concentration were discussed in detail, and a general equation was developed to describe the variation of surface ion concentration over time. A damage-based ion transport model was developed based on the damage evolution of the dynamic elastic modulus. The results demonstrated that the damage-based ion transport model exhibited excellent accuracy in predicting the ion transport behavior in the RAC. Furthermore, the mechanism of the effect of RCA on ion transport is more complex and requires a comprehensive study. This study provides theoretical support for the application of RAC in engineering construction and the calibration of important physical parameters in related numerical studies.