The feasibility of Witwatersrand gold tailing as an alternative in cement manufacturing as a possible contributor to the circular economy

Abstract

Throughout mining history, there have been growing concerns about tailing storage facilities. Concerns include the vast space tailings occupy, and their mismanagement resulting in environmental impact and health implications. Tailings form the highest percentage of material remaining post extraction of mineral, which subsequently requires a deposition site. Only a small percentage of tailings is used in backfill filling in underground operations. The study investigated the viability of gold tailings as an alternative in cement manufacturing and in doing so contribute to the circular economy. The framework of this study used the Witwatersrand Supergroup gold tailings from the Klerksdorp area in North-West Province, South Africa. The mineralogical, chemical, and physical properties of the Witwatersrand gold tailings were investigated and compared to the Ordinary Portland cement and Hexi gold tailings in Shandong Province, China. The Witwatersrand gold tailings in this study had a noticeably lower calcium oxide content (0.98%) than what is required in cement manufacture (63.68%). The aluminosilicate minerals were reasonably high (above 70%) resulting in a pozzolanic nature, which implies that a certain percentage of the gold tailings can be used as supplementary cementitious material in the production of cement mortar. The study also explored ways of reducing or eliminating the identified hazardous substances such as cyanide and radioactive elements. The concentration of uranium radioactivity in Klerksdorp gold tailings is 931.6 Bq /kg above the regulatory limit of 500 Bq/kg for uranium in cement manufacturing. The uranium radioactivity iii concentration can be reduced by incorporating a process of uranium extraction during gold extraction operations. Additionally, the South African policy on the valorisation of mining waste which only recognizes the retreatment of tailings under the Environmental Authorization under the National Environmental Management Act No. 107 of 1998 should be amended by including the use of mining wastes in other sectors of the economy through the circular economy framework.