Construction chemicals specialist CHRYSO Southern Africa supplied its CHRYSO® CWA 10 integral waterproofing admixture at the Temba Waterworks project undertaken by Group Five Civil Engineering. The readymix supplier for the project was Chromecrete.

Deon Klopper, technical sales consultant CHRYSO Southern Africa, says that the contract award vindicated a lengthy testing process that ultimately resulted in “a few mixes and products” being approved. The most important in this regard was CHRYSO® CWA 10, an admixture formulated specifically for water retaining structures. The total concrete work on the project was 17 000 m3, of which 14 000 m3 contained CHRYSO® CWA 10 in the mix.

Klopper explains that when CHRYSO® CWA 10 is added to concrete a chemical reaction with water results in the formation of long, narrow crystals that fill in the pores, capillaries and hairline cracks of a concrete mass.

“The crystals effectively block the pores rendering the concrete dense and waterproof, as well as maintenance free and durable,” Klopper says. CHRYSO® CWA 10 is used mainly in concrete subjected to hydrostatic conditions.

The dosage rate is typically 0.8% of the cementitious content of an approved mix design. CHRYSO® CWA 10 is compatible with other admixtures and supplementary cementitious materials and will not affect the workability or entrained air content.

“It transforms an entire concrete structure into an impermeable water barrier with lasting integral waterproofing properties,” he says.

CHRYSO Southern Africa manufactures and distributes two integral waterproofing products, namely CHRYSO® CWA 10 and CHRYSO® Fuge B. These products are added directly to the concrete mix at the time of batching. “Integral waterproofing is therefore a permanent solution as it is distributed uniformly throughout the concrete and not just on the surface,” Klopper explains.

The major benefit is that it reduces the permeability of concrete structures, which means that the concrete is more durable. Concrete with a low permeability can significantly reduce the risk of frost damage, acid and sulphate attack, steel corrosion, alkali aggregate reaction and efflorescence. Klopper explains that CHRYSO’s integral waterproofing admixtures all reduce water absorption and/or the passage of water through the hardened concrete.

CHRYSO® Fuge B is a pore/capillary blocking admixture. It combines with components of the concrete, effectively forming deposits which line the walls of the pores and capillaries and as a result thereof water ingress is effectively eliminated. It is mostly used in non-hydrostatic conditions.

Although not classified as an integral waterproofer, CHRYSO® Pareflo 20 is used in bricks, blocks and roof tiles to specifically reduce efflorescence caused by moisture that conveys calcium hydroxide through the capillaries in porous concrete to the surface.

“These admixtures are a simple and effortless means to introduce integral waterproofing into concrete. They are added directly to the concrete, mixed and placed on site, with no need for surface preparation or excavation. This not only speeds up the construction process but reduces labour costs as well as improving quality,” Klopper concludes.