There was cause for concern when areas of poor quality concrete were discovered at two of the thickeners and one clarifier at Exxaro’s Grootgeluk Coal Mine in Ellisras, Limpopo, where the consulting engineering company ARUP had no hesitation in specifying Sika products, including one of its polyurea membranes, to solve the problem by protecting and waterproofing the walls of the mine.
There was cause for concern when areas of poor quality concrete were discovered at two of the thickeners and one clarifier at Exxaro’s Grootgeluk Coal Mine in Ellisras, Limpopo. The consulting engineering company ARUP had no hesitation in specifying Sika products, including one of its polyurea membranes, to solve the problem by protecting and waterproofing the walls of the mine.
Exxaro is the second-largest coal producer in South Africa. The company’s main priority, the Grootgeluk Medupi Expansion Project (GMEP), was initiated to construct two new processing plants and to expand existing pits at the Grootgeluk Mine, which has since begun supplying coal to Eskom’s Medupi Power Station. Aveng Grinaker, a multi-disciplinary construction and engineering firm, was awarded the main contract, with BKV Holdings as sub-contractors.
As a moisture barrier, SikaGard-720 EpoCem ZA was applied at a minimum thickness of 2mm to the concrete walls. This three-part, epoxy-modified, cementitious, thixotropic, fine-textured mortar can also be used as a levelling layer over concrete, as a pore sealer, and as a levelling and smoothing layer for walls and covings in the food industry.
Providing easy, fast application and excellent protection of concrete particularly in aggressive environments, SikaGard-720 EpoCem ZA is impervious to liquids but permeable to water vapour. It bonds extremely well to green or hardened concrete, whether damp or dry, contains no solvents and can be applied by spray pump machine.
Requiring minimal waiting time, SikaGard-720 EpoCem ZA was coated with Sikalastic-EP Primer II, a two-part, low viscosity, epoxy-polyamine resin. This multi-purpose product is easy to apply, provides high bond strength, good penetration and short waiting times. It may also be used to prime cement screeds, metal and plywood, and is a primer for all PUR and polyurea systems.
As a waterproofing and protective coating on the concrete walls, Sikalastic-844 XT Plus, a two-part, flexible, modified polyurea membrane, was the product of choice. It is specifically designed for use in applications on concrete or steel where exposures to high acidic or alkaline chemical concentrations are present.
It also provides high resistance to microbial waste, so it is suitable for use in wastewater and treatment plants. Primary and secondary containment, petrochemical storage, fertiliser plants, food-processing plants and industrial floors and splash zones are more examples of where this versatile product may be used.
Sikalastic-844 XT Plus, which is 100% solids with zero VOC, is designed for machine application only. Its fast reactivity and cure time, as well as its monolithic and seamless protection, are significant advantages.
The initial suggestion was to coat the entire inside area of the two thickeners with Sikalastic-844 XT Plus, but Exxaro specified that only certain areas, totalling 500m2, should be coated. Although the Sikalastic 800 range of products provides such versatility with hundreds of different uses, it was specifically the high performance of Sikalastic-844 XT Plus in this application that allowed engineers and architects to recognise that it is not merely a solution to waterproofing, but actually a specialist product.
Contractors were faced with severely high surface temperatures, as the project took place during the hottest months. They also had to exercise extreme caution not to cause damage to the surrounding environment due to the site being situated in a sensitive ecological area.
Despite these challenges, the concrete refurbishment at Exxaro’s Grootgeluk Mine was another highly successful Sika project.
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