Effect of lithium slag dosage on macroscopic properties and hydration of cement pastes: a comparative study of OPC, UPC, and CSC systems

Investigating the effects of lithium slag (LS) as an admixtures on the properties of different cement pastes can expand its potential applications in construction materials. This study examines the influence of LS content (0%, 10%, 20%, and 30%) on the performance of ordinary Portland cement (OPC), ultra-fine ordinary Portland cement (UPC), and calcium sulfoaluminate cement (CSC) pastes. The underlying mechanisms are explored using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results indicate that incorporating LS reduces the fluidity, setting time, and bleeding rate of cement pastes but enhances their compressive strength at 1, 7, and 28 days. Specifically, LS improves the long-term strength of OPC pastes, whereas it primarily enhances the early-age strength of UPC pastes. For CSC pastes, LS significantly promotes both early and later-age strength. SEM, XRD, and FTIR analyses reveal that the effects of LS stem from a filling effect and the activation of hydration reactions, where reactive components and gypsum in LS promote the formation of hydration products such as calcium silicate hydrate (C-S-H) and ettringite. These findings provide a theoretical basis for the application of LS in diverse cementitious systems.