The Witwatersrand’s gold tailings are currently being re-mined to retrieve gold that previous technologies could not extract. Gold reclamation from tailings poses an opportunity to use Mine Waste as raw material in other fields such as construction. Due to the element composition of tailings, this can be used as aggregates and cement substitutes for concrete. This contribution takes advantage of the mining reclamation processes happening along the west rand to produce bricks and concrete for 3D printed houses that will then be fitted back into the immediate urban fabric surrounding the tailing in an interdependent operation of input-output.
The Witwatersrand, Johannesburg’s gold basin, crosses the city from West to East. Historically its landscape has been dominated by mine dumps. However, nowadays most of these tailings are being re-mined to retrieve the gold that old technologies could not extract. The west rand, especially, the section referred to as the Soweto cluster, is now under a project for its re-mining. Remining brings new opportunities for raw materials apart from gold and other precious metals. Gold sand dumps and slime dams are rich in minerals such as SiO2, Al2O3, CaO and Fe2O3, which make them very attractive for the production of construction materials since these oxides are the main constituents of cement as well as of key alkali-activated binders. This map shows the main tailings within Soweto’s proximity. The project seeks to create a network of Mine Waste cement-based products such as bricks and 3D printed houses as a solution for the housing shortage and the increasing backyarding practices in the area. The raw material in the tailings will be transformed and fitted back into the city’s growth.
From Retrieval to Product
Vlakfontein 238 IQ
These section shows the re-mining process of the tailing located in Vlakfontein 238 IQ farm. The re-mining process can be done through various methods, in this case, the re-mining process will be done using hydraulic mining monitors which consist in high-pressure water guns. The guns erode the tailing from the dry heaps, washing the material downstream where it is collected in a reservoir. The water guns diameter used range from 4 to 8 in and can retrieve between 100,000 to 350,000 dry tons per month per gun. The processing gold facility for the project, will process 100,000 tons a month.
After reaching the reservoir, the material is then pumped to the gold processing plant, where gold and other heavy metals will be separated from the material to then be dewatered and transported for its processing at the cement plant. The new cement will be used in the production of cement blocks and concrete for 3D printed houses, that will be distributed throughout Soweto and the city.