Mass transport properties of recycled aggregate concrete under coupling the action of chloride salt attack and uniaxial tensile loading

Abstract

Water and chloride permeability are two important parameters for the evaluation of recycled aggregate concrete (RAC) durability. In service, the tensile loading plays an extremely important role in the generation and propagation of microcracks inside the RAC. Thus, aiming at understanding the mass transport properties of RAC under the coupled action of chloride salt attack and uniaxial sustained tensile loading, an improved experimental set-up was self-designed. And then a series of tests involving the effects of different uniaxial sustained tensile stress levels (10%, 30% and 50% of ultimate tensile stress, namely λt = 0.1, 0.3 and 0.5) and different replacement ratios of recycled coarse aggregate (RCA) (0, 30%, 50% and 100% mass replacement of normal coarse aggregate, namely R0, R30, R50 and R100) on the transport properties of RAC were conducted, and their coupling effects were further analyzed. Generally, the results indicate that both the sorptivity and chloride diffusion coefficient of RAC increase with the increase of RCA replacement ratio and tensile stress level. The synergistic effect of RCAs and tensile stress significantly accelerates the process of water and chloride invasion into concrete. The initial sorptivity of R100 specimens at λt = 0.5 was about 4.44 times that of R0 specimens without loading. Moreover, the chloride diffusion coefficient exhibits a linear relationship with the RCA content, while it has a quadratic relationship with the tensile stress level.