Medupi Power Station

In May 2013, a large Sika project commenced at Eskom’s Medupi Power Station in Lephalale, Limpopo. Engineers at Nyeleti Consulting specified numerous specialist Sika products for repairs and protection of various areas of the plant. Contractors, BKV Holdings in a joint venture with Multi Contracts Specialists were subcontracted for the application of Sika products, which included supporting products for substrate preparations, and final coating products from the Sikagard and Sikalastic 800 series.

For general crack repairs, Sikadur-52 ZA, a low viscosity injection liquid based on high strength epoxy resins, was used. It not only forms an effective barrier against water infiltration and corrosion-promoting media, but also structurally bonds the concrete sections together. For filling of severe pinholes and blowholes as well as crack repairs, the thixotropic, structural two-part adhesive and repair mortar, Sikadur-31 CF Normal, was applied. This versatile product offers numerous advantages; easy to mix and apply, suitable for dry and damp concrete surfaces, very good adhesion, hardens without shrinkage, impermeable to liquids and water vapour, and good chemical resistance.

SikaGard-720 EpoCem, a three-part, epoxy modified, cementitious fine-textured mortar was used for reprofiling and as a moisture barrier. This thixotropic product is easy to apply and provides excellent protection of concrete, particularly in aggressive chemical environments.

Once surface preparations were complete, engineers decided that a 200m2 external sump floor would be the first area to be coated with the Sikalastic-841 ST system. The area was first primed with Sikafloor-161, an economical, low viscosity epoxy resin providing good penetration and excellent bond strength. To reduce pin holing and to create better mechanical key, a layer of Sikadur-931 Sand was applied as broadcast over the primer.

A coating of Sikalastic-841 ST was then machine sprayed over the sump floor. This elastic, pure polyurea membrane, suitable for waterproofing and anti-corrosion applications on concrete, steel and many other substrates, is UV resistant and provides excellent crack-bridging properties. Sikalastic-841 ST is applicable in temperatures from -15o to 70o and performs in constant temperatures from -30o to 120o. 100% solids with zero VOC, it is suitable for use in a wide variety of applications and its fast reactivity and cure time allows for almost immediate return-to-service time.

Upon completion and inspection of the sump floor, engineers were so impressed with this system that it was decided to use Sikalastic-841 ST as the primary coating system for all major areas at the plant, instead of Sikagard-63N, as originally specified. These major areas include the Water Treatment Plant, consisting of all internal and external sumps, all primary containment areas, backwash trenches and pump stations 1 and 2; the Fuel Oil Off-loading Area and the Fuel Oil Storage Areas.

A second product used from the Sikalastic-800 range, was Sikalastic-844 XT, a modified polyurea membrane with very similar properties to Sikalastic-841 ST. It is designed for seamless protection of concrete or steel where exposure to high acidic or alkaline chemical concentrations, are present.

Acid dosing areas in the Water Treatment Plant were coated with Sikagard-69, a plural component system, containing a proprietary polymeric binder that provides excellent performance in highly corrosive, chemical and abrasive environments. Designed for industrial use at elevated temperatures, it will maintain its physical properties under continued exposure at high constant temperatures. Its fast-curing, trowel grade consistency allows for back-to-service within 24 hours.

This huge project is still ongoing with almost 10 000m2 having already been coated with Sika’s outstanding products. Once fully operational, Medupi Power Station will be the fourth largest coal plant in the world and the biggest dry-cooled power station in the world.