Effect of limestone and sulfate on the uptake of chloride and isosaccharinic acid by high-slag cement paste (CEM III/C)

Abstract

The impact of SO42-and NaCl on the uptake of 36Cl-and isosaccharinic acid (ISA) by high-slag cement paste (CEM III/C) in the presence of CaCO3 was evaluated with systematic batch sorption experiments. The addition of CaCO3 resulted in a slight decrease in 36Cl-uptake, in line with previous studies. Enhanced sulfate concentration in the pore solution outcompeted 36Cl-sorption, resulting in very low distribution ratios (Rd). The increase in Rd at high NaCl concentrations is explained by the formation of Friedel's salt, confirmed by XRD and TG-DTA. ISA uptake remains unaffected in the presence of CaCO3, SO42-and NaCl, suggesting a differential sorption mechanism for 36Cl-and ISA. NaCl and ISA alter the pore solution composition, increasing [Ca] and [Si] as a result of the incongruent dissolution of cement hydrates. The impact of ISA is more pronounced due to the formation of complexes Ca-ISA.