Evaluating the functionality of different kimberlite mine wastes as alternative to building material

Abstract

Kimberlite diamond mines tend to produce vast amounts of rock-derived waste that are ultimately stored and rehabilitated at high cost to the mining company. Diamond mine rock waste does not always contain the same cocktail of hazardous elements typically associated with other mining commodities' rock waste. Repurposing this material in a creative, optimised way could lead to value creation. Instead of rehabilitation, this project suggests that using various types of rock waste could replace aggregate or other components in the manufacture of building-related products. This could allow mining companies, building material manufacturers and the local community to work together to produce an environmentally friendly and economically viable product. Previous studies have found that kimberlite waste could be used in a range of products, from aggregates to cement to clinker bricks and more. The few studies that have been done have mostly concerned themselves with local bureau of standards requirements, using various testing methodologies. This project investigates mine rock waste from five Southern African sites, examining 25 different materials. The tests conducted followed the South African Board of Standards (SABS) and other key quality bureau methods to assess compliance for a safety-critical product, with a focus on aggregate compliance tests due to time constraints. Information from different textural tests, aggregate impact value (AIV), chemistry (XRF), and mineralogy (XRD) helps assess the potential usage of 25 different materials. Results showed that all materials met SANS 1083/1090 density requirements, but most tailings failed on grading, fineness modulus and dust content due to excessive fines. Waste rocks graded well and achieved acceptable Aggregate Impact Values. Mineralogy was the dominant limiting factor: high phyllosilicate and clay content made most tailings and waste rocks unsuitable for concrete aggregate. Only a dolomite-dominant group and a feldspar/pyroxene-rich Voorspoed group showed conditional potential. Unsuitable materials often contained clay or phyllosilicate minerals suited to light aggregate or clay brick production, a viable beneficiation pathway.