Modeling of Chloride Transport Resistance in Cement Hydrates by Focusing on Nanopores

Abstract

This study proposes reasonable models to evaluate chloride ion ingress in cementitious materials with dense micropore structures. Salt water immersion tests with mortar specimens, including low water-to-cement (W/C) ratio materials, were conducted. The results show that chloride ion ingress is so slow in specimens with low W/C ratios that existing models cannot follow experimental trends, and pores in the nanometer range may have significant effects on the total extent of chloride ion transport. Two phenomena related to chloride ion ingress in nanopores were considered and installed in the existing system: a threshold radius regarding the chloride ion movement, and a reacting friction force along the pores against the water movement pressure. Measured chloride ion distributions with salt water immersion tests were used to verify the proposed models. By conducting additional numerical simulations, the possible mechanisms of high resistivity against chloride ingress were studied.