Chloride binding of early CO2-cured Portland cement-fly ash-GGBS ternary pastes

This paper compared the chloride binding of Portland cement pastes with and without early CO2 curing and examined the effects of FA and GGBS on the chloride binding of early CO2-cured cement paste. The results show that the chloride binding capacity of early CO2-cured Portland cement paste is much lower compared to the ones not subjected to early CO2 curing, and the former can be better described by Langmuir isotherm while Freundich isotherm is more suitable for the latter. The chloride binding of Portland cement-fly ash-GGBS pastes subjected to early CO2 curing mainly depend on the physical adsorption by C-S-H while the chemical binding related to the formation of Friedel's salt is extremely weak. The incorporation of FA and GGBS declines the chloride binding capacity of the Portland cement paste subjected to early CO2 curing due to lack of calcium hydroxide. However, the chloride binding of Portland cement-fly ash-GGBS pastes subjected to early CO2 curing are improved when CaCl2 solution is applied as soaking solution, which mainly comes from the enhancement of physical adsorption. The cation ions of chloride solution show little influence on the formation of Friedel's salt.