Utilization of ladle furnace slag as cement partial replacement: Influences on the hydration and hardening properties of cement

Abstract Ladle furnace slag (LFS) is a potential new resource for the preparation of cementitious materials with early hydration activities. To evaluate the application performance of LFS as a supplementary cementitious material, the effects of LFS on the hydration and hardening performance of cement were studied from the aspects of the hydration process, the physical and mechanical properties, the microstructure of the hardened paste, and the volume stability. The results showed that LFS has a significant setting acceleration effect and micro-expansion effect on cement. The blended cement containing LFS and ordinary Portland cement (LFS-OPC) had a better hydration product structure, mechanical strength, and volume stability at a low dosage (≤10%) of LFS. LFS with a high content (10%–30%) had a significant acceleration setting effect on the cement system, and the C3AH6 and AFm contents were high in the ultra-early stage (1 d), which were the main source of the ultra-early mechanical strength of the cement system. However, the strength and volume stability of the LFS-OPC with a high content of LFS were poor in the middle and late stages. It was also found that the hydration process of the LFS-OPC system could be divided into two distinct stages: the early hydration of aluminate minerals, such as C12A7 and C3A, and the later hydration of silicate minerals, such as C3S. With the increase in the LFS content, the hydration heat release rate of first stage of the blended cement increased significantly, indicating that LFS has the hydration characteristics of aluminate minerals. As a supplementary cementitious material, LFS has an excellent early hydration reaction activity.