Effect of dosage of lithium slag powder on the microstructure and hydration of ultra-low water-to-binder ratio lithium slag-based concrete prepared by microwave pre-curing

The excessive incorporation of lithium slag (LS) can negatively impact the performance of concrete. To improve the industrial utilization of lithium slag in concrete applications, this study explores the feasibility of producing ultra-low water-to-binder ratio lithium slag-based concrete (ULW/B-LSC) through microwave pre-curing. The experimental results indicate that concrete samples containing 50 % LS, when subjected to microwave pre-curing, achieved a compressive strength of 136.58 MPa after 28 days. In comparison, the ULW/B-LSC mix with 100 % LS attained a compressive strength of 77.43 MPa under similar curing conditions. Infrared thermography analysis demonstrated that the incorporation of lithium slag powder facilitated a more uniform temperature distribution during the microwave curing process, effectively reducing the risk of localized overheating. Microstructural investigations, including scanning electron microscopy (SEM) and nanoindentation test, further revealed that the inclusion of 50 % lithium slag contributed to the development of a denser microstructure. Notably, the interfacial transition zone (ITZ) width of the 50 %-lithium slag ULW/B-LSC decreased by 68.9 % after microwave pre-curing, in comparison to ULW/BC under standard curing conditions. In conclusion, microwave pre-curing proves to be highly compatible with ULW/B-LSC.