TECHNICAL
A WATER-WISE STEP ON YOUR WAY TO SUSTAINABILITY
Responsible contractors have realised the growing strain on SA’s scarce water resources and a new admixture is geared to conservation efforts with its waterreducing admixtures for concrete. A recent example of this was in the construction of the Vlakfontein Reservoir near Standerton, Mpumalanga. This is probably one of the largest cylindrical posttensioned concrete reservoirs in the world, with an inner diameter of 154m and a heavily reinforced 11,8m-high wall. A DYNAMIC MIX According to Patrick Flannigan, technical manager of the concrete business unit at Chryso Southern Africa, the project made use of several admixtures to reduce water and improve workability. “One of these is our Plast Omega 178 plasticiser, which – when used in a concrete mix – permits a reduction in water content without affecting the consistency, also referred to as the workability,” he says. “It can also increase the slump – or flow – without affecting the water content of the mix.” The Vlakfontein Reservoir has a groundwater drainage system constructed with three layers of 5MPa no-fines concrete. The 8 000m3 of no-fines concrete comprises a 50mm-thick layer of 9,5mm stone mix, followed by a 245mm and 125mm layer of 19mm aggregate.
Evaporation was controlled using Chryso’s Profilm 19 evaporation reducer at the Khutsong Reservoir project.
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To facilitate consistency and ensure that the aggregate would bind mechanically and hydraulically, Chryso’s Easydrain was introduced to these mixes for the cement paste. This specialised admixture
SOUTH AFRICAN BUILDER DECEMBER 2021
