Chloride diffusion behavior of engineered cementitious composite under dry-wet cycles

Abstract

This study investigated the chloride diffusion behavior and mechanism of engineered cementitious composite (ECC) under dry-wet cycles and NaCl immersion. A standard chloride diffusion test was conducted to evaluate the effects of water-to-binder ratio (w/b), NaCl solution concentration and exposure time on the chloride diffusion depth, content and coefficient in ECC prisms. The microstructures of chloride-eroded ECC were also characterized using X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that the chloride diffusion depth, content, and coefficient were decreased with w/b increasing. The increment of dry-wet cycle number facilitated chloride erosion but reduced late diffusion coefficient and rate. Moreover, the increased chloride concentration made the chloride diffusion depth and content ascend, while its effect on apparent chloride diffusion coefficient was marginal. After 15 dry-wet cycles, Ca(OH)2 in ECC matrix was gradually consumed and Friedel salt and CaCO3 were formed on the chloride diffusion surface. In addition, the porosity of ECC was reduced by decreasing macropores/voids and increasing mesopores under dry-wet cycle. ECC exhibited the worst resistance to chloride diffusion under dry-wet cycles.