Alkaline solidification of gold mine tailings for production of lightweight masonry blocks

Abstract

South Africa is the world’s largest gold resource. This is due to the substantial amount of gold that exists in the Witwatersrand Basin. The processing of gold leads to the production of gold mine tailings. Gold mine tailings are generated from mineral processing of gold ore through which gold is separated. Mine tailings are generally waste materials and are normally disposed of in slurry form in storages constructed on huge areas of land, these storage facilities are called tailings dams. This study was conducted to strengthen and stabilize gold mine tailings by alkaline activation to produce masonry blocks that can be used for building and construction as per minimum requirements for ASTM C34-13, C129-14a and South African standard (SANS227: 2007). The effect of variation of Solid to liquid (S/L) ratio, NaOH concentration and temperature on the UCS was investigated. This was achieved by treating the gold mine tailings with NaOH solution. The feasibility of using gold mine tailings to produce lightweight masonry blocks was studied by conducting unconfined Unconfined Compressive Strength (UCS) tests, SEM imaging, and XRF and XRF analysis. The alkaline activation of Gold Mine Tailings (AU MT) at a S/L ratio of 14.31% and 9 M concentration had higher UCS than those produced at 3 M and 6 M. Curing temperature is an important factor affecting alkaline activation and the UCS of masonry block. The UCS increases with the curing temperature up to a certain level and then decreases with the curing temperature. For the AU MT herein, the optimum curing temperature was found to be 80 °C with bulk density of 1578 kg/m3. The AU MT based masonry block meet ASTM standards they can be used for building and construction purposes such as the building of structural clay load bearing wall tiles of all C34-03 ASTM designation grades and building blocks of ASTM designation C6210, type NW (negligible weathering) with the minimum UCS of 10.3 MPa.