Contribution of layered double hydroxides to hydration and chloride binding capacity of OPC-SAC-GGBS repair materials

Chloride erosion is an important reason for the deterioration of reinforced concrete constructions. The aim of this research is to explore a new approach of hindering the migration and diffusion of chloride ions in cement-based repair materials through layered double hydroxides (LDHs). CaAl-LDHs was synthesized by co-precipitation method, and the structure and adsorption kinetics of CaAl-LDHs were characterized by simulated adsorption experiments, SEM, XRD, FTIR and TGA. The mechanical properties and hydration characteristics of OPC-SAC-GGBS containing LDHs were investigated, and the dynamic change process of the chloride content in paste with erosion time was revealed. The results indicate that the maximum adsorption of chloride by the synthesized LDHs was 43.5 mg/g, and the adsorption process was fitted by quasi second-order kinetics and Langmuir model. LDHs promoted the early hydration of pastes and enhanced the binding ability for chloride ions. The chloride binding ability of the composite paste was not significantly affected by the long-term erosion. Therefore, LDHs has a promising application for the inhibition of chloride attack in reinforced concrete and demonstrates the necessity of dual protection of reinforced concrete structures by improving the chloride binding capacity and permeability resistance.