Effect of lithium slag as supplementary cementitious material on sulphate attack resistance of cement mortar

This study investigated the effect of using lithium slag (LS) as a supplementary cementitious material (SCM) in improving the resistance against sulphate attack of cement mortar exposed to a 5% Na 2 SO 4 solution. The LS content ranging from 20% to 60%, were evaluated over 180 days through visual inspection, compressive strength tests, ultrasonic pulse velocity (UPV) measurements, mass change analysis, expansion monitoring, and microstructural characterisation. The results revealed that incorporating LS as SCM significantly enhanced the resistance to sulphate attack with higher replacement suggesting better performance. Mortars blended with LS showed improved strength and compactness, reduced cracking, lower mass change, and minimal expansion. All LS blended mortars displayed less than 0.1% expansion, while the control specimen exhibited 0.36% expansion. The microstructural analysis confirmed that LS mitigates the formation of expansive ettringite and gypsum and thus reduces the crystallization pressure. The 60% LS mixed mortar exhibited no visible damage and the lowest reduction in compressive strength (13.18%). However, the 40% LS mixed mortar showed the highest compressive strength due to its compact microstructure and balanced hydration products. Although 60% LS content offered better sulphate resistance, 40% proved to be the optimal balance of durability and mechanical performance. These findings underscore the potential of LS as a sustainable and efficient SCM for enhancing sulphate resistance. • LS as SCM significantly mitigate the formation of AFt and gypsum • Higher replacement (40-60%) poses better performance • LS blended mortars displayed less than 0.1% expansion