Properties of Cement Based Materials Containing Copper Tailings

ABSTRACT: Increasing demands for copper and copper allied products have made the processing of low grade ores with high volume waste output unavoidable. Presently, billions of tons of copper tailings can be found in major copper producing countries. This study explored the possibility of using these copper tailings either as a cement replacement or additive material in pastes, mortars and concretes of 0.65, 0.57 and 0.50 w/b ratios. Fresh properties of mixtures such as paste consistencies and setting times, mortar yield stresses and flow losses, and concrete slumps were studied. The mechanical properties investigated were compressive strength, flexural strength, splitting tensile strength and abrasion resistance. The durability properties evaluated were autoclave and sulfate expansions, acid and chloride penetration resistance, rapid chloride permeability, accelerated corrosion and half-cell potential (HCP) tests. Finally, visual inspection of reinforcements after corrosion tests, toxicity characteristic leaching (TCLP) test and cost analysis were also performed. Results showed that dry copper tailings affect mixture consistency negatively. However, the use of pre-wetted tailings reduced this drawback. Compared to mortar and concrete mixtures containing copper tailings as a cement replacement material, enhanced mechanical strengths much better than those of the control samples were obtained from mixtures containing copper tailings as an additive. Improved durability properties were also observed in mixtures containing copper tailings. Leaching of toxic metals from concretes were below the US Code of Federal Regulations (CFR) limits. Considering all these test results and cost analyses, the use of pre-wetted tailings at 5% addition level by mass of cement seemed to be the best reuse approach. Keywords: Copper tailings, environment, pastes, mortars, concretes, mechanical strength, sulfate and acid attack, chloride penetration, accelerated corrosion, leaching. ……………………………………………………………………………………………………………………………………………………………………………………………………………………