Effect of Sepiolite@MgAl-LDH Core-shell Materials on Chloride Transport Resistance of Cement Mortar

The high degree of agglomeration of layered double hydroxides (LDH) nanosheets poses a significant challenge to the application of LDH as chloride absorbents in cementitious materials. To address this issue, this study attempts to grow LDH on the surface of sepiolite using an in-situ synthesis via co-precipitation. The effect of the as-synthesized sepiolite@MgAl-LDH core-shell materials (SEP@LDH) on the chloride transport resistance of cement mortar is evaluated via rapid chloride migration (RCM) and chloride natural diffusion tests. Additionally, the microstructural characteristics of the as-synthesized sepiolite@MgAl-LDH core-shell materials and cement mortar were analyzed. The findings demonstrate that, compared to pure LDH and sepiolite, the as-synthesized SEP@LDH exhibits a markedly larger specific surface area. Additionally, the SEP@LDH substantially improves the chloride retention capacity of the cement relative to pure LDH. Furthermore, the incorporation of SEP@LDH markedly improves the chloride migration resistance of the cement paste. This enhancement can be ascribed to the improved chloride retention capacity of the highly dispersed LDH and the enhanced pore refinement in the cement mortar resulting from the addition of SEP@LDH.