Study on the leaching performance of chromium (Cr) and cadmium (Cd) from the utilization of solidified nickel slag as concrete floors

With the increasing demands on more metals extraction, the hazardous waste resulted from mining industry has also raised. In this paper, the treatment process of nickel slag containing hazardous metals is described. The treatment involved a solidification process, where nickel slag is used as fine aggregates substituting agent. This study aimed to determine the optimum dosage of nickel slag that met specification in the construction of concrete floors. A series of technical feasibility test were carried out by replacing the weight proportions of sand with nickel slag gradually from 0% to 100% to examine the compressive strength, absorption rate, durability and leaching performance. The results indicated that even though all mixture variations possessed high value of absorption rate indicating high permeability concrete mix, all mixtures, however, had good durability. Furthermore, based on the compressive strength test, a mixture with 60% substitution of nickel slag is considered as a viable replacement of sand in the concrete floors construction in conformance to American Concrete Institute. The leaching performance test showed that leachability of heavy metals content, particularly Cr and Cd from mortar specimens were below the standard according to Indonesian Government Regulation No 101 of 2014, therefore, in terms of environmental point of view, the utilization of solidified nickel is considered safe to be used as concrete floors