It has been a challenge to reuse and recycle the Basic Oxygen Furnace (BOF) slag for steel companies worldwide. Due to the existence of f-CaO in slag, the volume of slag expands during hydration, limiting the uses of BOF slag. Accordingly, removing f-CaO to prevent BOF slag from expansion is the key for slag utilization. Despite many post-treatments of BOF slag having been tried, none of them have proved to effectively decrease the amount of f-CaO/MgO. Consequently, the core technology, namely, hot stage BOF slag modification (HBM), was developed by China Steel (CSC) to solve the volumetric expansion problem. By treating BOF slag with HBM technology, a reaction with f-CaO/MgO and silica was done to form calcium/magnesium silicates so that the volumetric expansion of the slag was inhibited. Currently, the success rate of the BOF slag modification is higher than 96% after refining several experimental parameters during HBM operation. Besides slag modification, it is equally important to utilize the modified slag as raw materials for road construction, concrete-based materials as well as asphalt concrete aggregates etc. Herein, pavement / grass bricks and concrete-based revetment blocks were made by using modified BOF slag as a raw material. The performance of the pavement bricks, such as compressive strength, is higher than 70 MPa. Most importantly, the volumetric stability of bricks and revetment blocks was examined. The stability of the modified BOF slag-based products was revealed after testing them outdoors for at least 8 months. Further volumetric stability outdoor tests of these concrete products is ongoing. In addition to conventional uses, novel applications of modified BOF slag (e.g. ceramic tiles) are being developed. On the basis of results aforementioned, we believe that the development of BOF slag modification technique at CSC will shed light on the utilization and reuse of BOF slag.
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