Sustainable use of ferronickel slag fine aggregate and fly ash in structural concrete: Mechanical properties and leaching study

Abstract

Ferronickel slag (FNS) is a by-product of nickel production that is used as an alternative fine aggregate. This study evaluates the workability, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity and chemical leaching characteristics of concrete containing FNS from garnierite ore and fly ash. It was found that 50% replacement of natural sand by the FNS resulted in a well graded fine aggregate and maximized the strength development. The 28-day compressive strengths of the concrete mixtures containing 50% FNS were 66 MPa and 51 MPa for no fly ash and 30% fly ash respectively. The splitting tensile strength, flexural strength and modulus of elasticity of concrete containing 50% and 100% FNS correlated well with the compressive strength, which is similar to the correlation for concrete containing 100% natural sand. The equations of design Codes and Standards are found conservative in the prediction of these properties from a specified compressive strength when FNS is used as a replacement of natural sand. The FNS was found environmentally compatible since leaching of heavy metals were far below the regulatory limits. Therefore, the combined use of FNS and fly ash is considered as a promising alternative in the production of green concrete for structural applications.