CEMENT & CONCRETE
Stemming leaks on a tailings thickener
D
ue to major water losses, the 60 m diameter tailings thickener at Pilanesberg Platinum Mine (PPM) required resealing to make it watertight. Sika was contacted by main contractor Leoka Project Management for a solution. In turn, ConSolve Civils was asked by Sika to assist Leoka as the subcontractor. PPM’s owner, Sedibelo Platinum Mines, required an urgent repair since the thickener is the ‘heartbeat’ of the mine and production losses were substantial. Con-Solve Civils assessed the repair requirements and recommended that the old bandages and joint sealant be removed and totally replaced. The Leoka engineering team supported the proposed solution and Sedibelo instructed Con-Solve Civils to proceed with the necessary repairs. Under normal circumstances, this would have been an approximate six-to-eight-week project, but by working 12-hour day and night shifts, ConSolve Civils completed it in just 2.5 weeks. In terms of product diversity, and volume, a variety of Sika products was specified and used. Sikaflex-11 FC, a multipurpose elastic adhesive and joint sealant, was applied to all construction joints as the secondary seal before installing Sikadur-Combiflex SG as the primary joint seal. Forty-seven
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IMIESA April 2022
6 kg Sikadur-31 DW kits were used as the bedding mortar for the bandage system. Sikadur-31 DW is a two-part epoxy structural adhesive that has been specially formulated to meet the requirements for use in contact with drinking water. It was best suited for this time-sensitive project, as it is easy to mix and apply, has high mechanical strengths and good abrasion and chemical resistance.
Waterproofing tape As part of the Sikadur Combiflex SG System, 188 m of Sikadur-Combiflex SG-20 P – 2 mm x 250 mm was used to waterproof the wall-to-floor joint, while 848 m of SikadurCombiflex SG-20 P – 2 mm x 200 mm was used to waterproof floor joints. Sikadur-Combiflex SG-20 P is a flexible waterproofing tape based on modified flexible/thermoplastic polyolefin, with advanced adhesion properties. Other advantages in the use of this product include not requiring site activation, high flexibility (a useful property for crack and joint bridging), and good resistance to chemicals and UV exposure.
Twenty-five kits of Sikalastic-152, a highly elastic cement-based coating, were applied on the wall joints incorporating a 5 mm x 5 mm plastic-lined glass-fibre mesh, as well as next to the Sikadur-Combiflex SG on the floor joints for additional waterproofing due to small surface cracks that formed on the concrete. It was also applied over wall construction joints with applicable plastic-lined glass-fibre matting for additional reinforcement. One month after the thickener was filled, the structure was certified watertight.
