Eleven products from specialist chemicals company Sika have been used in the refurbishment of platinum producer Impala Platinum’s (Implats’) Rustenburg operations, a 14-shaft complex in the Bushveld Igneous Complex near Rustenburg, which was completed in June.

Since this active platinum processing facility could not afford stoppages, the project was carried out under a highly restrictive schedule, with some work only being performed during scheduled plant shutdowns.

“Further challenges at the complex included a closed working environment and limited access to certain working areas,” adds Sika, noting that it was credit to its products, many of which meet the most stringent international standards, that the lengthy project at the world’s second-largest platinum producer, remained on schedule with no major delays incurred.

According to the Durban-based company, the products were specified by engineers from Blue Consult for a scope of work that included general concrete repairs, spalling repairs, external reinforcing, waterproofing, and protection. The contract to complete the refurbish- ment was awarded to concrete repair and corrosion specialists Hindle Mason Projects.

“For general concrete repairs, Sikagrout-212, a high performance, cementitious grout, was used. The grout remains easy to apply, as it has an adjustable consistency. The fluid grout also expands by generating gas while in the plastic state of curing and remains noncorrosive with high final strengths,” Sika states in a June press release.

The company adds that for larger-scale structural repairs, its free-flowing, high strength cement-based microc oncrete Sikacrete-214 was used. With a maximum aggregate size of 9 mm, Sikacrete-214 is an economical option, as it provides “excellent” adhesion and high resistance to freeze/thaw cycling.

“Sikacrete-214 is shrinkage compensated and provides rapid strength development. Therefore, it is ideally suited for casting sections or members where the volumes required are too large for conventional grouts or too small and inaccessible for normal concreting procedures,” Sika notes.

Corroding rebar at the Implats complex was first grit blasted and, subsequently, coated with SikaTop Armatec-110 EpoCem, a cementitious, three-component epoxy resin bonding primer with corrosion inhibitors. As this product boasts Sika’s EpoCem technology, it allows “excellent” adhesion to concrete and steel, as well as extended open times for repair mortars, says the company. SikaTop Armatec-110 EpoCem can be applied by brush or spray gun and provides high-shear strength as well as good resistance to water and chloride penetration.

For spalling repairs to columns and beams, cement-based, multipurpose patching and repair mortar Sika Rep LW was applied.

The company explains that Sika Rep LW has “excellent” adhesion and nonsag properties, and is shrinkage compensated, permeable to water vapour and provides a high resistance to the freeze/thaw cycling.

Prior to structural strengthening of the actual storage silos, the strength and ductility of Implats’ support columns were increased by applying Sikadur-330, a two-part, thixotropic epoxy-based impregnation resin, followed by SikaWrap-230 C, an unidirectional, woven carbon fibre fabric designed for installation using the dry application process.

Further, Sikadur-30 was used as a structural adhesive for bonding Sika CarboDur plates onto silos and external reinforcement. Sikadur-30 is a high strength, two-part, thixotropic adhesive based on a combination of epoxy resins and special filler.

The product hardens without shrinkage and provides high abrasion and shock resistance. The Sika CarboDur plates are manufactured from a pultruded, carbon- fibre-reinforced polymer and, according to Sika, these “world-renowned, high-strength laminates are extremely durable with outstanding fatigue resistance”.

“Despite their robustness, Sika CarboDur plates are lightweight, easily transported and very simple to install. The numerous combinations of high strength and the modulus of elasticity available, makes this exceptional product highly versatile,” the company notes.

Prior to the end of the project, about 3 500 m of Sika CarboDur plates S512 had already been installed on the silos.

Another structure at the mine that required refurbishment was the main clarifier. Here, Sika protected the interior surface with Sikagard-720 EpoCem, a three-part, epoxy modified, thixotropic, fine-textured mortar. The product provides better chemical resistance than polymer cement concrete mortar.

“Sikagard-720 EpoCem is impervious to liquids, but permeable to water vapour, and provides an excellent bond to green or hardened concrete, whether damp or dry,” the company adds.

Along with the addition of Sikagard-720 EpoCem, a final protective coating was added to the interior of the clarifier, which was also primed with the company’s Sikafloor-161 low-viscosity epoxy resin. This was followed by a coating of Sikalastic-841 ST pure polyurea liquid, which was applied to the membrane.

“Importantly for this project, Sikafloor-161 requires short waiting times, while the very fast reactivity and curing time of Sikalastic-841 ST, allowed for almost immediate return to service.”