Environmental protection remains a critical point of contention for South Africa’s industrial sectors. The mining and construction sectors in particular deal with immense amounts of natural resources, where one unearths billions of tonnes of aggregate annually, and the other uses massive quantities of rock, clay, limestone, and gravel for the cement, bricks, and asphalt needed to erect buildings, lay roads, and construct critical public service infrastructure.
However, there is a method by which these two industries can, through close cooperation and strict adherence to South African National Standards (SANS) and other relevant internationally recognised standards, greatly limit their impact on the environment and establish a circular economy that ensures the least earth goes to waste.
Companies such as the Gap Infrastructure Corporation (GIC), which utilises vast amounts of building material during large public infrastructure projects, have a significant need for the kinds of raw waste material that mining companies offload to mine dumps after the valuable ore has been extracted. A unique opportunity potentially exists to reclaim this precious material and use it to help government in its goal to turn South Africa into a construction zone over the next few years.
Mining aggregate applications in construction
With the proper processing, mine tailings can serve as a valuable source of aggregate for construction materials that would otherwise constitute quarrying large swaths of land. It would be particularly useful as road base layers, foundation backfill, and brick and concrete production.
Tailings sand can directly replace natural sand in concrete or asphalt, with a particle size and chemical composition comparable to conventional crushed sand. Coarse tailings can serve as fine aggregate in concrete, while finer tailings can be compacted or converted for use as a road sub-base.
When graded and compacted, coarse tailings and waste rock can also be used as structural filler material in embankments, berms, levees, and other earthworks, providing the shear strength and density required for stable highway and rail foundations. Additionally, large, durable waste-rock fragments can be sized for riprap or gabion stone, offering effective erosion protection for riverbanks, bridge abutments, and coastal revetments in place of quarried armour rock.
Clay-rich tailings can be mixed with cement or lime as binders to produce pressed bricks or paving blocks. Tailings with high clay content provide plasticity and cohesion, which are beneficial for forming bricks or blocks, with the fine particles assisting in achieving a compact structure when pressed.
Finally, fine tailings sand has proven suitable for 3D-printed concrete mixes, supplying the particle-packing and flow properties needed for layer-by-layer construction in quickly developing automated building systems.
The biggest benefit is on the environment
Mine tailings remain a serious environmental problem, with no widely effective solution yet implemented at a meaningful scale.
Moreover, the bulk of construction materials, such as bricks and cement, depend on energy-intensive quarrying that damages the natural environment. While construction waste cannot completely replace quarrying, it can supplement and take considerable pressure away from the sector by utilising waste that’s produced during the mining process.
Because the rock has already been broken and ground at the mine, utilising it for construction material partly avoids or limits the fuel-hungry crushing, blasting, and long-haul trucking that normally accompany fresh quarrying. Every tonne of tailings that takes the place of virgin aggregate leaves another hillside intact and saves on thousands of litres of diesel – savings that multiply across housing estates, road upgrades, and water networks.
Finally, fewer truckloads tipped onto a dump mean slower waste dam expansion, lower risk of structural failure, and less toxic dust drifting across to neighbouring settlements. As volumes decline, vast tracts of land once quarantined for perpetual storage can be reformed, top-soiled, and re-seeded, possibly restoring habitats over decades instead of centuries.
Combined, the benefits are immeasurable for the health of the environment and prosperity of future generations. While it might be difficult to establish the relationships, protocols, regulations, supply chains, and other structures necessary to achieve this goal, the results could be more than worth the effort for future generations.
