Experimental Study and Numerical Analysis of Chloride Ion Diffusion in Hydrotalcite Concrete in Chloride Salt Environment

Hydrotalcite, known as layered double hydroxides (LDHs), is a new type of admixture used to delay the corrosion of reinforcement. The aim of this study was to investigate the chloride ion diffusion behavior of C30 concrete with varying amounts of calcined hydrotalcite (0%, 2%, 4% and 6%) in a chloride salt environment. The NT-Build 443 test was adopted to characterize the one-dimensional accelerated chloride ion penetration of concrete. The distribution of chloride ion concentration in hydrotalcite concrete with different mix proportions immersed in sodium chloride solution for 30 days and 60 days was determined, and the chloride ion diffusion coefficient and surface chloride ion concentration were fitted based on Fick's second law to establish the chloride ion diffusion model considering the influence of multiple factors. This model was validated using COMSOL Multiphysics finite element software. The results show that concrete mixed with LDHs can meet its compressive strength requirements and that the resistance of concrete with 2% calcined hydrotalcite to chloride ion penetration is the best with a 19.6% increase in the 30-day chloride ion penetration coefficient. The chloride ion diffusion process under chloride salt immersion conditions is in accordance with Fick's second law. The chloride ion concentrations calculated with COMSOL software and the test results are in good agreement, which verifies the reliability of the chloride ion diffusion model.