AfriSam is playing a pivotal role in the construction of one of the largest and most technically complex water towers in the key South African economic hub, Gauteng.
The southern African construction materials major is supplying specially designed readymix concrete to meet both structural and seismic performance requirements.
Located near Main Reef Road, south of Johannesburg, the 43m-high water tower will store 3.2 megalitres of water to support the new Goudrand mega-city development.
With construction led by M&D Construction and engineering design by SCIP Engineering Group, the project has demanded highly customised concrete solutions from AfriSam. The structure is located in a seismically active zone and required additional reinforcement in the lower section of the shaft to withstand ground acceleration above 0,1g. This called for increased steel density and a concrete mix that could deliver strength, flowability and controlled heat of hydration.
AfriSam’s product technical team leader, Mduduzi Ndlovu, explains that the concrete mix was developed with a high proportion of supplementary cementitious materials (SCMs) to reduce the heat generated during curing. “The base mix comprised 70% ground granulated blast furnace slag (GGBS) and 30% AfriSam High Strength Cement, reducing the ordinary Portland cement (OPC) content to just 20%,” says Ndlovu. “Despite the low OPC content, the mix exceeded expectations – achieving the target strength of 51 MPa was achieved in only 28 days in relation to the designed 56-day requirement.”
The construction process placed high demands on the readymix in terms of both slump control and delivery precision. With over 210 kg of rebar per cubic metre in some sections, AfriSam developed a high-slump pump mix for vertical pours, while limiting the slump to 130 mm in slanted sections to prevent concrete from sliding off the shuttering.
