Bacteria fixing CO2 to enhance the volume stability of ground steel slag powder as a component of cement-based materials aiming at clean production

Steel slag is a by-product in the process of steel manufacture. It has caused huge environmental pressure. The use of steel slag as the admixture of cement-based materials is an effective way to enhance clean production. But the poor volume stability caused by dead burned lime and periclase in steel slag is a crucial factor restricting its utilization. Some research has shown that carbonization could convert dead burned lime and periclase into carbonate. But the carbonization rate and carbonization degree were low. The objective of this paper is to adopt Bacillus Mucilaginosus (BM) to absorb carbon dioxide to promote the carbonization of dead burned lime and periclase, thereby enhancing steel slag utilization in cement-based materials. The effects of BM on the carbonization rate and degree of dead burned lime and periclase were studied by conducting experiments; the influence of BM on the stability of steel slag mortar with different particle sizes was studied. The results show that BM can reduce the apparent activation energy of the carbonization reaction of dead burnt lime and periclase, and increase the reaction rate and maximum reactivity. MIP (Mercury Intrusion Porosimetry) analysis found that steel slag mortar specimen with BM had a lower porosity than that without BM. The autoclaved linear expansion rate of the steel slag mortar specimen with BM can meet standard requirements while that without BM cannot. It is indicated that the addition of BM can effectively promote the carbonization of dead burned lime and periclase in steel slag and solve the problem of poor volume stability of cement-based materials caused by steel slag. This research helps to improve the utilization of steel slag as an alternative binder to cement and alleviates the environmental pressure caused by the storage of waste steel slag.