Properties of the Cement Paste Mixed with Various Types of Aluminum Sulfate Based Liquid Alkali-Free Accelerator

In this paper, the effects of various components in alkali-free accelerator on the setting of cement paste were studied, and the morphology of the hydrates during hydration was investigated with SEM. The experimental results show that the aluminum sulfate, diethanolamine and hydrofluoric acid can effectively shorten the setting time of cement paste, while excessive dosage has minimal impacts on the setting time. The diethanolamine and hydrofluoric acid can not only shorten the setting time but also can improve the stability of the accelerator. It was evidenced by the SEM that the aluminum sulfate accelerates cement coagulation by quickly forming a large amount of ettringite in the cement paste. The results in this study suggest that the shortest setting can be achieved when the dosage of aluminum sulfate, diethanolamine and hydrofluoric acid in a liquid alkali-free accelerator is 57 %, 5 % and 5.7 % , respectively.