As if Eskom didn’t have enough production woes, when the main conveyor at the Kendal Power Station burnt down, transportation of coal to the plant was cut off and so was the production of electricity. Repair of roads, bridges and cooling towers was urgently set in motion and Sika was called on to supply a large quantity of the materials needed to get the Mpumalanga power station at Kendal back up and running.

Currently the largest coal-fired power station in the world, Kendal Power Station has six Units and outputs 686 Mega Watts per Unit. Just one of the Units had to be switched off while these repairs to the Conveyor were made. Kendal supplies between 15% and 20% of South Africa’s power demand. Interestingly, of all the power stations in South Africa, Kendal is the only one where a switch can be “flipped” to start it up - all the others take approximately 7 days to start up.

Both the client and the contractor trust Sika’s products and are very satisfied with the installation by contractor Hindle Mason Projects (HMP).

Products & Quantities

Sika MonoTop-615 HB was used to repair the burnt concrete which had become brittle and started spalling. Approximately 7,500 kg of this high build cementitious, polymer modified, one component repair and reprofiling mortar containing silica fume, was used in conjunction with SikaTop-Armatec110 EC . The advantages of using Sika MonoTop-615 HB is that it only requires mixing with water; has excellent workability characteristics, adjustable consistency and excellent thixotrophic behaviour, making it especially suitable for overhead and vertical applications. In addition, it has good mechanical strength and freeze/thaw resistance and is able to withstand water and chloride penetration.

Approximately three hundred 1.75 litre packs of SikaTop-Armatec110 EpoCem were used in conjunction with the Sika MonoTop-615 HB as a bonding agent for the concrete and an anti-corrosion coating for the reinforcement steel embedded in the concrete. This cement-based, epoxy –modified three-component product has excellent adhesion to steel and concrete and acts as an effective barrier against the penetration of water and chlorides. It also contains corrosion inhibitors, has a high degree of mechanical strength, and provides an excellent base for subsequent applications of cement and epoxy cement based repair mortars. Its added advantage is that it may be spray applied, making it a versatile product that can be used in difficult situations.

As usual, the concrete that had been chipped away for repair and replacement was of varying thicknesses, not only in those areas which had burnt and become brittle, but also in other sections of the station. Sika Rep LW, one of Sika’s ready to use cementitious repair mortars specifically designed for non-sag patching on deteriorated concrete, was used in those areas where a thin layer of material was needed, while the Sika MonoTop-615 HB described above, a “High Build” that has aggregate added to it to make it thicker, was used for the thick layer concrete repairs.

Sika MonoTop-620, a cementitious one component polymer modified pore sealer and leveling mortar containing silica fume, was also used for the concrete repairs, the thickness of the underlying concrete governing which of the three products was used where. Sika MonoTop-620 is a thin layer trowel applied mortar for sealing pore holes and honeycombing. It is particularly good for repairing defects and reprofiling imperfections in both vertical and horizontal surfaces.

The base plates holding the stilts on which the coal-carrying conveyor runs were also burnt, causing the conveyor to fall and rip the bolts out of the base plates, which then had to be reset. SikaGrout-212, a non-corrosive, expansive cementitious grout for the structural grouting of machine and column base plates, bearing plates, precast wall panels, crane rails and anchor bolts, as well as for concrete repairs, came to the rescue. SikaGrout-212 was the perfect product for this because it is an easy to use, ready to mix powder with an adjustable consistency and very good flow characteristics. It shows rapid strength development and delivers high final strengths, expanding by gas generation whilst in the plastic state of curing. Afterwards, 176 bags of Sikagard-550W Elastic were applied as a plastic-elastic protective coating for the newly repaired & existing concrete on the conveyor trusses, to protect it against weathering and deterioration from the aggressive environment.

This messy and varied project, which required lots of little “odd jobs”, could have proved a real headache for the client and contractors. Fortunately, HMP had already been on site for a previous contract, and as soon as the problem arose they were called back. They in turn automatically chose Sika products, which they knew were reliable and versatile enough to get the coal conveyors back on track, and electricity back in our homes, with Sika once again helping to fulfill ‘basic human needs’.