In an endeavor to increase water supply to match the rapidly growing population of Gauteng, Johannesburg Water decided on a substantial expansion to its Driefontein Wastewater Treatment Works.

It was during this expansion project that Sika’s repair and rehabilitation products played a key role.

Concrete walls were primed with SikaTop-Armatec 110 EpoCem, a cement-based, epoxy-modified three component, anti-corrosion coating and bonding agent that provides an excellent bonding coat for subsequent applications of Sika repair mortars.

With excellent adhesion to steel and concrete, it acts as an effective barrier to water and chlorides.

As steel reinforcement protection, Sika MonoTop-610, which meets the ZTV-SIB requirements for corrosion protection, was applied.

It forms a bonding-slurry for the MonoTop-615 HB, a high build repair and reprofiling mortar containing silica fume.

This mortar was used on the sections of walling requiring thick layer concrete repairs and, with its excellent thixotropic behaviour, is especially suited for vertical and overhead applications.

Patching power

Sika Rep LW, a non-sag, cement-based, multi-purpose patching and repair mortar, was used wherever cosmetic or structural repairs were necessary.

Just as easy to mix and apply as the MonoTop products, Rep LW provides excellent adhesion, is shrinkage compensated, permeable to water vapour and has a high resistance to freeze/thaw cycling.

Smoothing things out

As part of the concrete protection on the plant’s clarifiers and pump stations, three solvent-free products were used.

Sikagard-720 EpoCem is a three-part, epoxy-modified fine-textured mortar for leveling and finishing of concrete, particularly in aggressive chemical environments.

It is impervious to liquids but permeable to water vapour and forms an excellent bond to either green or hardened concrete, whether damp or dry.

It is the ideal preparation for smooth surface finishes and can be applied by spray pump machine. Once the easy and fast application is complete, a minimum waiting period is required prior to application of other resin-based Sika coatings.

The final protection layer on the clarifiers, including launders, valve chambers and pump stations was achieved with applications of Sikagard-63 N, an abrasion resistant, two-part, liquid-proof epoxy resin coating designed for normal to highly aggressive chemical environments.

The Driefontein Waste Water Treatment Works is one of the oldest facilities of its kind and caters for the communities in northwestern Johannesburg.

The expansion will see its present capacity of 30Ml/day increasing to 55Ml/day and will allow for future expansion to 80Ml/day.