A multi-phase model for predicting the effective chloride migration coefficient of ITZ in cement-based materials

Mortar microstructure is considered as a three-phase composite material, which is cement paste, fine aggregate and interfacial transition zone. Interfacial transition zone is the weakest link between the cement paste and fine aggregate, so it has a significant role to determine the properties of cementitious composites. In this study, specimens (w/c = 0.35, 0.45, 0.55) with various volume fractions of fine aggregate ( f V = 0, 0.1, 0.2, 0.3 and 0.4) were cast and tested. To predict the equivalent migration coefficient ( e M ) and migration coefficient of interfacial transition zone ( itz M ), double-inclusion method and Mori-Tanaka theory were used to estimate. There are two stages to estimate and calculate the thickness of interfacial transition zone ( h ) and migration coefficient of interfacial transition zone ( itz M ). The first stage, the data of experimental chloride ion migration coefficient ( s M ) was used to calculate the equivalent migration coefficient of fine aggregate with interfacial transition zone ( e M ) by Mori-Tanaka theory. The second stage, the thickness of interfacial transition zone ( h ) and migration coefficient of interfacial transition zone ( itz M ) was calculated by Hori and Nemat-Nasse\'s double inclusion model. Between the theoretical and experimental data a comparison was conducted to investigate the behavior of interfacial transition zone in mortar and the effect of interfacial transition zone on the chloride migration coefficient, the results indicated that the numerical simulations is derived to the itz m M M ratio is 2.11~8.28. Additionally, thickness of interfacial transition zone is predicted from 10m, 60 to 80m, 70 to 100mand 90 to 130mfor SM30, M35, M45 and M55, respectively.