The Performance and Mechanism Analysis of Cement Pastes Added to Aluminum Sulfate-Based Low-Alkali Setting Accelerator

Abstract

We proposed a type of low-alkali liquid state setting accelerator, named HLSA; it was environmentally friendly product. To investigate the temperature adaptation and cement flexibilities of HLSA, the setting time and strength development properties of cement with HLSA were discussed in this paper. The effects of HLSA on hydration process, hydration products, and microstructure were studied by means of X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP). The results show that four typical 42.5-grade ordinary Portland cement types with 6–8% HLSA could satisfy the first-grade requirements according to JC477-2005 even at a lower temperature (e.g., 10°C). Further, the percentage ratio of 28 d compressive strength of cement with 6–8% HLSA was over 90%; the XRD diffraction peak of AFt integrated area of cement with 7% HLSA was 3818 at 5 min of hydration; SEM observation revealed that AFt crystals were filled in the pore of cement at 28 d of hydration; the temperature adaptation and cement flexibilities of HLSA were excellent; the cement with HLSA coagulating in a short time attributed to promoting the formation of abundant AFt and the hydration of C3S.