LAUSR

Abstract This study investigated the potential of calcium aluminate cement (CAC) to solidify/stabilize Cr(VI) (Na2CrO4). The hydration and microstructure development of CAC pastes in the presence of Na2CrO4 were examined by means of isothermal calorimetry, XRD, TG/DTG and SEM-EDS. The leaching properties of Cr(VI) were evaluated by TCLP and GANC methods. The results demonstrated that addition Na2CrO4 significantly retarded the early-age hydration of CAC depending on the dosage, while caused an acceleration of long-term hydration. The formations of CAH10 and C2AH8 were inhibited, instead AH3, CrO4-C3AH6 and CrO4-U phase were found as the main hydrates. These changes of hydrate assemblages led to a strong decrease in compressive strength. Complying with the TCLP regulatory limit of 5 mg/L, up to 1.0% of Cr(VI) could be effectively immobilized in the CAC paste. Two binding phases, CrO4-C3AH6 and CrO4-U phase, were responsible for controlling Cr(VI) leaching in the CAC pastes.