Study on the reaction mechanism of lithium slag from different production processes in supersulfated cement

Developing green building materials helps promote ecological sustainability. In this study, low-alkali lithium slag (LLS) and high-alkali lithium slag (HLS) were used to partially replace anhydrite in the preparation of supersulfated cement (SSC). The performance of the SSC prepared with the two types of lithium slag (LS) was investigated by examining both individual systems and their comparative behaviour. The results revealed that the two LS systems exhibited common features: (1) satisfactory strength was achieved when the dosage was less than 19 %; (2) the gypsum content increased initially but then decreased, with a peak observed between 7 h and 12 h; and (3) in the LS-based SSC, both C–S–H(II) and C–S–H(III) were identified, with partial substitution of Si by Al. Distinct differences were also observed. LLS promoted the early formation of AFt, whereas HLS retarded AFt formation in the early hydration stage, leading to delayed AFt development but enhancing the generation of hydration products at later ages. In addition, substitution of Si by S and Al, and Ca by K and Na, was observed in the C–S–H phase of the HLS system. With increasing curing time, AFt crystals became coarser, and the porosity gradually decreased; the overall porosity of the HLS system was lower than that of the LLS system. Moreover, hollow tubular AFt structures were detected in the LLS-7d sample. • Supersulfated cement (SSC) was prepared using high-alkali and low-alkali lithium slag (HLS and LLS) as substitutes for anhydrite. • HLS based SSC exhibited higher late-age strength, achieving a compressive strength of 63.4 MPa. • LLS accelerated the early formation of AFt, whereas F - in HLS delayed AFt formation. • The presence of K + and Na + in HLS enhanced pore filling, leading to a denser.