PERFORMANCE of CONCRETE INCORPORATING NICKEL SLAG AND GOLD TAILINGS AS PARTIAL REPLACEMENT MATERIALS

Abstract

The growing scarcity of natural sand and the increasing environmental cost of cement manufacturing have led to a growing interest in the use of industrial by-products as constituents of concrete. This study investigates fine nickel slag (FNS) and gold tailings (GT) as partial replacements for fine aggregate and cement, respectively, in conventional concrete, with the dual objective of reducing mining and metallurgical waste generation and reducing pressure on virgin resources. In Indonesia, the minimum compressive strength of concrete for residential use is 21 MPa. The possibility of fulfilling this criterion to the advantage of the environment and economy was investigated by replacing 5-25% of the cement and sand with GT and FNS. Having characterized the physical and chemical characteristics of the raw materials, six concrete mixes, a reference, and GT5 to GT25, were made and evaluated for workability, compressive and tensile strength, porosity, and gas permeability. Workability was drastically reduced with the substitution levels. The slump value decreased from 80 mm for the control mix to 26 mm for 25% replacement. Similarly, compressive strength decreased, but the best result among the replaced mixes was GT5, with 38.03 MPa at 28 days, comfortably exceeding the Indonesian requirement. The tensile strength also exhibited a similar decreasing pattern, with the maximum reduction at 25% replacement. In summary, it is proposed that FNS and GT may be implemented in the standard concrete manufacturing with acceptable structural performance and therefore provide a more sustainable and waste-conscious method.