Effect of Lithium Sulfate on the Hydration Mechanisms and Performance of Ferroaluminate Cement

The effect of lithium sulfate (LS) admixture on the performance of ferroaluminate cement (FAC) remains poorly understood, and no systematic investigation of the regulatory effects of LS hydration in FAC systems has been conducted. By revealing how LS modulates the macroscopic properties and hydration progression of FAC, this work addresses an important knowledge deficit in the existing literature. This study investigated the performance evolution of FAC pastes with varying amounts of LS addition. It examined the setting time, fluidity, compressive strength, pH and electrical conductivity of the pore solution, as well as X-ray diffraction (XRD) and electrical resistivity. The findings indicate that LS significantly accelerates the early hydration rate of FAC, shortening setting time and reducing paste fluidity as its content increases. Notably, LS inhibits compressive strength development at 12 h, yet it enhances the rate of strength development after 1 day. The analysis of electrical conductivity and pH demonstrated that LS increases ion concentration and alkalinity within the first day, and these parameters stabilize after 28 days. Resistivity measurements indicate that LS raises paste resistivity within 3 h and enhances the peak hydration rate. Quantitative XRD demonstrates that LS induces complex lithium–sulfate coupling effects on ettringite (AFt): LS20 hits the critical Li+ inhibition threshold, while the sulfate from the higher LS dosage mitigates such negative influences. These findings establish a theoretical foundation for the targeted application of LS in materials based on FAC.