Transforming Waste into Strength: Innovative Use of Carbon-Sulfur Industrial Waste as Supplementary Material on Concrete

The Indonesian nickel mining industry is currently experiencing very significant development due to increasing global demand. This condition was responded to by Indonesia as a country with large nickel reserves to continue to intensify nickel downstreaming, with the hope that Indonesia would become not only the largest nickel commodity producer in the world but also a producer of processed nickel products. On the other hand, the increasing activity of the nickel ore processing industry and the production of nickel products, such as massive nickel mining activities, can also pose threats and negative consequences for the community and the environment in the mining area and its surroundings. In nickel mining, especially in the smelting nickel ore process, sulfuric acid is used through hydrometallurgical processes, forming Carbon-Sulfur as one of the wastes produced. Carbon-Sulfur waste, which contains 88% Sulfur, 11% CaO, and 1% Fe and Mn, is a mineral source that has the potential to be recycled or reprocessed, one of which is by making Carbon-Sulfur an admixture for civil engineering purposes such as concrete products. This research aims to determine whether Carbon-Sulfur waste from nickel mining can be reused and to test the effect of adding Carbon-Sulfur as an admixture in concrete products on improving the quality of the concrete. The results show that Carbon-Sulfur waste material has been tested as non-B3 waste so that it can be reused. Then, the compressive strength test results show that Carbon-Sulfur waste has the potential to increase the most optimal concrete compressive strength with an admixture composition of 2% and a curing period of 14, 28, or 90 days.