Alteration of cement rheological properties and setting-hardening: Novel insight into the impact of polyaluminum sulfate

The accelerator significantly influences the setting and hardening performance of shotcrete, in order to develop novel setting components, this study investigates the underlying mechanisms through which polyaluminum sulfate (PAS) facilitates the setting of cement paste. QXRD, Isothermal calorimetry, Zeta potential and Rheological test were employed to analyze the effects of PAS addition on the setting and hardening behavior, hydration kinetics, and rheological properties of cement paste. When the dosage of PAS is 10 %, the initial and final setting times are reduced by 54.39 % and 38.57 % respectively, meanwhile the compressive strength after 6 hours increases by 659.09 %. The influence of PAS on cement setting acceleration and rheological properties were analyzed using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the Water Film Thickness (WFT) theory. PAS leads to an acceleration in particle aggregation rate and an increase in shear stress and plastic viscosity of the cement paste. Furthermore, the accelerated hydration effect of PAS promotes the formation of additional hydration products, strengthens the interparticle connectivity, and facilitates the formation of a rigid network. This study highlights a novel pathway for understanding the rapid setting mechanism of aluminum-based accelerators.