Effects of sodium sulfate and potassium sulfate on the properties of calcium sulfoaluminate (CSA) cement based grouting materials

Abstract

CSA cement is usually used in grouting materials because of its fast setting and high early strength properties. This paper focuses on the effects of sodium sulfate and potassium sulfate on the hydration mechanism and properties of calcium sulfoaluminate (CSA) cement based double liquid grouting materials (DLGM). A comprehensive experimental program including XRD, TG-DTA, hydration heat, scanning electron microscope (SEM) and mechanical tests were performed. The results show that both sodium sulfate and potassium sulfate accelerated the hydration of CSA cement and the formation of ettringite from the very beginning and shortened the initial and final setting time of DLGM. The changing behaviors of setting time, hydration heat and strength of DLGM with sodium sulfate and potassium sulfate were found to be different and their optimum contents were also different. The microstructure observation shows that the addition of sodium sulfate made the ettringite merged as plate-like, and potassium sulfate generated longer ettringite strips stacked together in DLGM. By considering both setting time and compressive strength, the recommended adding amounts of sodium sulfate and potassium sulfate are 3% and 1.5%, respectively. These findings could contribute to the adjustment of physical properties of DLGM.