Sustainable utilization of copper tailings and tyre-derived aggregates in highway concrete traffic barriers

Abstract

Abstract In this study, the performance of multiple natural fine and coarse aggregate replaced concrete samples using copper tailings (CTs), fine and coarse tyre derived aggregates (TDA) in the construction of highway concrete traffic barriers were investigated. Cementitious properties of CTs were investigated. At low levels of replacement, Mindolo-CTs portrayed cementitious properties after the uniaxial comprehensive strength (UCS) at 28 days, because of that Mindolo-CTs was used simultaneously with natural fine and coarse aggregate replacement TDA. A UCS of 31.51 MPa was attained at 70% fine sand replacement with Mindolo-CTs and 8.74% of coarse aggregate (CA) replacement with tyre derived aggregate (C-TDA). UCS of 28.6 and 26.54 MPa was attained at 30% and 50% fine sand replacement with CTs, while fine-grained tyre derived aggregate (F-TDA) at 1.5% and 4% respectively. The heavy metal leachability of all samples was below their drinking water standard. The microstructure of the 28 days concrete samples was investigated by X-ray diffraction (XRD) test and Scanning electron microscope (SEM) test. XRD results depicted the presence of phlogopite in samples comprised of CT and TDA. SEM results showed that the reduction in the percentage of cement from 28.77% to 19.73% affected the rapid formation of hydration cryptographic phase of calcium silicate hydration (C-S-H) and Ettringite.