Effects of Cerium Concentration and Solvent on Physical and Chemical Characterization of Rapid Setting Cement

This study was conducted to explore the feasibility of rapid setting cement (RSC) as an agent of immobilization for certain elements such as fission products or radioactive materials through evaluation of the setting time, apparent porosity, bulk density, pH value, conductivity, compressive strength, and compositions. Two different cylindrical sample groups were created. The first group was a mixture of the cement powder with deionized water (DIW) and different concentrations of Ce (0, 2, 5, 7.5, and 10 wt%). The second group included the cement powder, artificial seawater (ASW), and same Ce concentration patterns. Samples were analyzed by X-ray diffraction (XRD), fluorescence analysis (XRF), and scanning electron microscopy including energy-dispersive X-ray spectroscopy. The results showed that the final setting time and compressive strength of RSC with both solutions (DIW and ASW) decreased as Ce content increased while opposite trends were observed for the apparent porosity and bulk density of RSC under the same concentration effect. As salt contents increased, the pH decreased while the conductivity increased gradually. The XRD patterns revealed that two newly identified phases were reported, namely CeAl₁₁O₁₈ and Ce_4.667 (SiO₄)₃O. The XRF results showed uniform distribution of Ce concentrations within RSC with both solutions (DIW and ASW). The morphology of matrix samples showed that the existence of Ce distributed on the pore wall or clustered with Si, Al, Mg, K, P, Fe, and O.