Influence of water scouring on chloride ion diffusion in rice husk ash recycled aggregates concrete

Abstract

This study investigates the chloride ion diffusion behavior in concrete incorporating rice husk ash (RHA) and recycled aggregates (RA) under water scouring conditions. The research results indicate that both free and total chloride ion concentrations in recycled aggregate concrete (RAC) exhibit an initial increase, followed by a subsequent decrease, as the distance from the concrete surface increases. The incorporation of RHA reduces both free and total chloride ion concentrations while increasing bound chloride ion content. However, an excessive amount of RHA can weaken the resistance of RAC to chloride ion penetration. Water erosion deteriorates the internal microstructure of RAC, accelerating the transport of free and total chloride ions. However, it does not compromise the chloride ion binding mechanism conferred by RHA. The fine particulate of RHA provides additional nucleation sites for cement hydration, while the reservoir effect ensures a steady supply of free water to these sites. This synergistic interaction enhances the pozzolanic reaction between cement hydration products and RHA, resulting in reduced Ca(OH)₂ content and increased formation of C-S-H gel.