Optimization of f-MgO/f-CaO phase in ladle furnace slag by air rapidly cooling

Ladle furnace slag (LFS) has great potential as a new type of cementitious material, but the important value has not been effectively used at present. One of the main reasons is that the over-burned free MgO (f-MgO) and free CaO (f-CaO) phases in LFS would cause the volume expansion of material. In this study, the f-MgO and f-CaO phases in LFS are optimized by air quenching treatment. It was found that size of f-MgO is reduced from 30 to 45 lm to 2.5-3.5 lm, which is about an order of magnitude lower. The f-CaO is distributed in the leaf-like morphology with smaller size in the range of 15-20 mu m. The MgO and f-CaO in air-quenched modified LFS (MLFS) can be dispelled in the early hydration stage. Compared with LFS, the volume expansion of blended cement with 20% MLFS is reduced by more than 10%, showing an obvious improvement effect on volume stability. (C) 2020 Elsevier B.V. All rights reserved.