Chloride diffusion behavior of coral aggregate concrete under drying-wetting cycles

Abstract

This study investigated the chloride diffusion behavior of coral aggregate concrete (CAC) under drying-wetting cycles. The influences of the aggregate type, strength grade, fly ash (FA) content, and basalt fiber (BF) content on the free chloride concentration in the concrete were determined. The apparent chloride diffusion coefficient (Dapp) of the CAC was calculated, and then used to analyze the instantaneous chloride diffusion coefficient (Dins) of the CAC. The test results showed that the free chloride concentration of the CAC was higher than that of ordinary aggregate concrete (OAC), with a smaller free chloride concentration for a higher strength grade. The Dapp and Dins first increased and then decreased with increases in the FA content and BF content. The Dins was 65 ~ 87% smaller than the Dapp. The time attenuation coefficient of the chloride diffusion coefficient had good positive correlations with the strength grade and FA content, and a good quadratic functional relationship with the BF content. The peak chloride concentration appeared at approximately 4 mm inside the concrete, and increased with the erosion time, which conformed to the power function law. In addition, a calculation model for the apparent chloride diffusion coefficient was established. The porosity of CAC can be effectively reduced when the FA content is 30% or the BF content is 0.1%, in addition, the chloride diffusion coefficient is positively correlated with the porosity.