Study on engineering properties of alkali-activated ladle furnace slag geopolymer

•The increased L/S dilutes the concentration of the alkali agent, which effects the engineering properties.•A higher amount of alkali agent yielded greater engineering properties.•Curing in saturated limewater promotes the polymerization reaction. Geopolymers, a new form of aluminosilicates, are environmentally friendly materials. These materials are produced from industrial wastes. This study, based on the industrial waste, Ladle furnace slag (LFS), employed an alkali-activated technology to activate LFS. The fixed alkali modulus ratio (SiO2/Na2O) was 1. LFS Geopolymer was prepared at different liquid/solid ratios (L/S) of 0.35, 0.40 and 0.45 and with different alkali agents of 4%, 6% and 8%. The LFS Geopolymer was cured under various conditions (air and saturated limewater) to evaluate the mixture and engineering properties of LFS Geopolymer at different ages. The results show that the workability of the LFS geopolymer increased with an increasing L/S and alkali agent. Moreover, the compressive strength and ultrasonic velocity increased with an increase in the alkali agent and a decrease in L/S, but the weight loss was reduced. Therefore, the appropriate use of alkali-activated technology can activate LFS, thereby enhancing its engineering properties. Curing in saturated limewater can greatly improve the engineering properties of the geopolymer compared to air curing. Specifically, the compressive strength of LFS increases by 5.4–58.9%, and the ultrasonic velocity of LFS increases by 0.84–22.9%. The thermal conductivity increases by 0.166–0.443W/m·K, and the overall shrinkage of LFS cured in the saturated limewater ranges between 0.0017% and 0.0342%, which is far lower than samples cured in air, thus indicating that curing in saturated limewater can effectively prevent LFS shrinkage.