World leader in specialty construction repair and protection products, Sika was unsurprisingly a winner at the Northern Wastewater Works project undertaken by Mndeni Structural Services, in Dainfern, Gauteng. In April 2010, MPA Consulting specified the use of Sikalastic-150, SikaGard-720 EpoCem ZA, Sikafloor-156ZA Primer and SikaGard-63N. The project required the rehabilitation of clarifiers used in the primary treatment process of waste water at these wastewater works near Diepsloot.

Since the two clarifiers are situated on top of 12-metre high reservoirs, gaining access to the only inspection hole at the cover of the structures was quite a task. An innovative solution was for scaffolding to be lowered in through the hole, followed by the workers who would be erecting the scaffolding inside the clarifier. Once inside, the application of the four specialist Sika products could begin in earnest - remaining mindful of the intense humidity parameters presented for the duration of the job.

SikaLastic-150, a highly elastic, cement-based waterproofing coating was used for its crack bridging properties and to prevent cracking on the outer surface of the reservoir. Once applied, the roof was covered with heavy-duty plastic sheeting during the curing phase, to avoid exposure to direct sunlight, which could lead to acceleration of the curing process. The product was applied to each reservoir alternately, allowing each coat to cure before moving on to the next. Each clarifier received five coatings alternately with a block brush to allow for drying.

Treatment of the surfaces included the use of Sikafloor-156ZA Primer, a two-part resin used for priming concrete before the application of levelling materials. This solvent-free primer has low viscosity and increases the durability of 20the hole, followed by the workers who would be erecting the scaffolding inside the clarifier. Once inside, the application of the four specialist Sika products could begin in earnest - remaining mindful of the intense humidity parameters presented for the duration of the job.

SikaLastic-150, a highly elastic, cement-based waterproofing coating was used for its crack bridging properties and to prevent cracking on the outer surface of the reservoir. Once applied, the roof was covered with heavy-duty plastic sheeting during the curing phase, to avoid exposure to direct sunlight, which could lead to acceleration of the curing process. The product was applied to each reservoir alternately, allowing each coat to cure before moving on to the next. Each clarifier received five coatings alternately with a block brush to allow for drying.

Treatment of the surfaces included the use of Sikafloor-156ZA Primer, a two-part resin used for priming concrete before the application of levelling materials. This solvent-free primer has low viscosity and increases the durability of the proceeding products applied to the surface.

SikaGard-720 EpoCem, a superfine epoxy-cement sealing mortar, and Sikagard-63 N, a solvent-free, highly chemical resistant coating, were both used on the inside of the reservoirs. As the clarifiers separate the water from the waste, it was only necessary to coat the upper level of the reservoir. The water is separated and pushed to the lower section and the waste remains on the upper level. Firstly a thin film of SikaGard-720 EpoCem ZA was applied as a moisture barrier, and, although not designed as chemical protection, it provides improved chemical resistance over concrete in harsh conditions. The final product application was Sikagard-63N, used to safeguard the structure against corrosion and weathering, and to protect the concrete from the methane ingress caused by the solid waste. Sikagard-63N was specified for the clarifiers as it is a liquid proof product ensuring that the concrete durability is not compromised under environmental strain.

The project was completed successfully with thanks to the expertise of Shaun Sadie and his team from Mndeni Structural Services, and the consistently high quality of Sika products and solutions.