Characteristics of ferrochrome slag aggregate and its uses as a green material in concrete – A review

Industrial wastes and by-products have been explored for many years as green construction materials. The use of some industrial wastes and by-products including ground granulated blast furnace slag, silica fume, and fly ash has already been standardized in several codes of practice as green construction materials. However, Ferrochrome slag (FCS) is one of the by-products that has not yet been standardized, particularly in concrete production. FCS is produced during the extraction of ferrochrome (FC) from the natural minerals. Due to its chemical composition, physical nature, and mechanical properties, FCS has recently attracted the researchers’ interest as an alternative green and sustainable construction material, particularly as a concrete aggregate. The review article summarizes the physical, chemical, and mechanical characteristics of FCS. The review also explores the beneficial utilization of FCS as a fine and coarse aggregate in the production of green and sustainable concrete. It is found that the physical and mechanical characteristics of the FCS aggregate are generally superior to the conventional aggregate. Although FCS aggregate contains a considerable amount of the hazardous element (i.e., residual chromium), it is substantially stable within the concrete mixture. Previous studies show that FCS coarse aggregate has a considerable effect on improving the strength and durability properties of concrete. However, the contradictory effects of using FCS fine aggregate on concrete properties were observed in different studies. Subsequently, more studies are needed to observe the effect of FCS fine aggregate on the mechanical and durability properties of concrete. In addition, the long-term safety and environmental compatibility of FCS containing concrete in diversified environmental conditions should critically be assessed in the near future.