Study on the effect of chloride ion ingress on the pore structure of the attached mortar of recycled concrete coarse aggregate

Abstract

In this study, based on the porous interface of recycled aggregates (RA), the effects of chloride ion (Cl−) ingress by drying-wetting cycles on the pore structure of recycled aggregate concrete (RAC) with a full replacement ratio under different temperatures conditions were investigated. Changes in the pore structure of the old and new mortars were determined by mercury intrusion testing. The surface morphology and morphological characteristics of the reaction products in the pores were observed via scanning electron microscopy. The results showed that the porosity, pore connectivity, fractal dimension and distribution of the pore size and pore volume were remarkably transformed by Cl− ingress. During the wetting phase, the products dissolved and migrated between the pores and crystallized during the drying phase, and the increase in temperature promoted this process. With the dry-wet cycles, the original pore space was gradually divided and filled, forming a large number of new pores with smaller pore sizes. The model of RA partition-interface Cl− ingress was presented based on the RA porous interface, and the mechanism of the effect of Cl− ingress by drying-wetting cycles on the pore structure of RAC was in-depth analyzed.