Using layered double hydroxides and anion exchange resin to improve the mechanical properties and chloride binding capacity of cement mortars

Abstract

Chloride-induced corrosion results in the deterioration of concrete structures. To resolve this issue, two types of synthetic layered double hydroxides (LDHs) 2D nanoflakes based on CaFe-NO3 and CaFeAl-NO3 and a strongly basic anion exchange resin (SBAER) were developed for removing chloride ions from simulated sea sand (SSS) mortars. We investigated the combined effect of SSS mortars blended with chloride adsorbents using the response surface methodology (RSM). A Box-Behnken Design (BBD) was used to discuss the independent variables (CaFe-NO3 LDHs, CaFeAl-NO3 LDHs, and SBAER) and evaluate the response of compressive strength and free chloride content concerning admixture content. Experimental results showed that the free chloride content of the samples decreased upon the addition of LDHs and SBAER due to a synergistic effect, which resulted in the formation of LDHs-Cl, [N+(CH3)3Cl−], Friedel’s salt (FS), and Kuzel’s salt (KS). The optimal range of the admixture content was determined to be 0.3–0.6 wt% CaFe-NO3 LDHs, 0.2–0.5 wt% CaFeAl-NO3 LDHs, and 0.2–0.5 wt% SBAER. In conclusion, LDHs and SBAER exhibited excellent chloride binding capacity, which makes them promising candidates for use as high-efficiency and stable chloride composite adsorbents in marine concrete.