Utilization potential of fly ash and copper tailings in concrete as partial replacement of cement along with life cycle assessment

Abstract

Fly ash (FA) and copper tailings (CT) both are, anthropogenic wastes, spread all over the globe due to rapid growth in thermal power plants and progressive increase in the demand of copper. This study examines the feasibility of combined utilization of FA and CT in concrete as a partial replacement of cement by assessing compressive strength, cost, and environmental impact. Morphology and constituent minerals of FA and CT have been identified to understand the utilization potential. Subsequently, the concrete has been designed for 30 MPa target strength as per IS 10262:2009 for different mix proportions of FA and CT. Improvement (up to 8.27% compared to the control mix) in the compressive strength has been observed at combined replacement of 10% FA and 5% CT. The cost of concrete can also be reduced up to 16% without compromising its compressive strength. The environmental impact assessment of the modified concrete mix proportions has also been performed using life cycle assessment (LCA) as per ISO 14040:2006. Effect of all raw materials, electricity, and water consumption have been considered from their cradle to grave approach. One cubic meter concrete has been taken as a functional unit in LCA. Notable reduction has been observed in the chosen midpoint categories up to 38% in climate change, up to 32.6% in human toxicity, up to 33.6% in ozone depletion, up to 31.9% in agriculture land occupation, water depletion up to 34.3%, fossil depletion up to 34.8%, particulate matter up to 35.4%, and metal depletion up to 25.2%.