Construction World February 2023

DAMS & RESERVOIRS

The Vlakfontein reservoir design included a permeable groundwater drainage system comprising three layers of 15 MPa no-fines concrete.

GETTINGCONCRETE PERFECT FORDAMS AND RESERVOIRS

Armand van Vuuren, Commercial Manager Export at CHRYSO Southern Africa.

Ensuring the integrity and constructability of key water infrastructure in the region, CHRYSO® Southern Africa is contributing its admixture solutions to

make the most challenging projects a success.

T his is according to Armand van Vuuren, Commercial Manager: Exports at CHRYSO Southern Africa who says that among these are two path-breaking reservoirs in South Africa’s Gauteng province: Vlakfontein reservoir, which is the largest cylindrical post-tensioned concrete reservoir in the country; and Khutsong reservoir, with Africa’s first round, prestressed raft floor to deal with dolomitic ground conditions. CHRYSO® Southern Africa is also working on the multi-million Euro project to reshape the plunge pool at the base of the Kariba Dam wall. Vlakfontein reservoir With an internal diameter of 154 m – about the length of one and a half football fields – the Vlakfontein reservoir holds over 210 Mℓ of potable water. The outer concrete walls are almost 12 m high, reaching about three storeys. It has a 200 mm thick

floor slab layer that consumed 1 800 m 3 of 35 MPa concrete. This had to be pumped in 13 separate pours of between 250 m 3 and 36 m 3 each. Van Vuuren says the project made use of CHRYSO® Plast Omega 178, a high-performance water reducing plasticiser, in all its concrete mix designs. “This reduced the water content of each mix to 175 ℓ/ m 3 while ensuring workability and strength,” he explains. “This admixture also increases the slump – or flow – without affecting the water content of the mix.” The concrete in the reservoir’s floor slab, wall footing and roof slab was augmented with CHRYSO® Serenis shrinkage inhibitor – to reduce shrinkage of the concrete. CHRYSO® CWA 10 crystalline integral waterproofing agent is also used to reduce the permeability of the concrete in the floor, walls and columns. “When moisture is present, this agent creates a reaction

28 CONSTRUCTION WORLD FEBRUARY 2023