Chloride penetration into recycled aggregate concrete subjected to wetting–drying cycles and flexural loading

Abstract

This paper presents the experimental results of chloride penetration into Recycled Aggregate Concrete (RAC) subjected to sodium chloride solution coupled with wetting–drying cycles and flexural loading. Detailed chloride profiles were tested by potentiometric titrimeter which show the variation of water-soluble (free) and acid-soluble (total) chloride contents in RAC. For purpose of studying the influence of coarse Recycled Concrete Aggregate (coarse RCA) on the chloride penetration, different replacement of coarse RCA were used by ranging from 0%, 30%, 50%,70% and 100% ratio by weight. Additionally, the effect of mineral admixtures and stress ratio on such penetration was studied. The chloride diffusion coefficient for RAC was calculated by the error function solution to Fick’s second law. The chloride binding capacity of RAC was also analyzed. Finally, X-ray computed tomography (X- CT) was used to estimate chloride transport progress in RAC for the first time. The results show that the chloride profiles in RAC is dependent on the mixtures and the flexural loading applied to the concrete. Coarse RCA induces considerable influence on chloride penetration in concrete. The addition of mineral admixtures makes concrete more compactness hinder chloride ions ingress into interior concrete. The increased magnitude of flexural loading results in higher chloride contents in RAC probably due to micro-cracks generated and extended. The influence of coarse RCA replacement and mineral admixtures on the chloride binding capacity is obvious, but the influence of stress ration is no regularity. The results of X-CT indicate that the solution does not transport through the old attached mortar in coarse RCA.