Chloride binding of cement paste containing wet carbonated recycled concrete fines

Abstract

The overall effect of wet carbonation recycled concrete fines (RCF) on the chloride binding capacity of cement paste was quantitatively decoupled into the effect of paste pH reduction, and the contribution of each component (uncarbonated phase, CaCO₃, silica gel) in the wet carbonated RCF. Results indicate that incorporating wet carbonated RCF decreases both the chemical and physical chloride binding capacity of the cement paste. The extent of the decrease in the former is significantly lower than that of the latter. The main factors determining the extent of the decrease in chloride binding capacity are the reduction of paste pH and the effect of silica gel. These two effects become significant with increasing carbonation degree of RCF, mainly with increasing carbonation time. Increasing the CO₂ flow rate during RCF wet carbonation effectively mitigates the negative impact on chloride binding capacity due to the increased aluminum content in the produced silica gel.