Afrisam is supplying specially designed readymix concrete to meet both structural and seismic performance requirements of a 44 m high water tower to support the new Goudrand mega city development near Main Reef Road south of Johannesburg.
With construction led by M&D Construction and engineering design by SCIP Engineering Group, the project has demanded highly customised concrete solutions from AfriSam. Storing 3.2 Mℓ of water, the structure is located in a seismically active zone and requires additional reinforcement in the lower section of the shaft to withstand ground acceleration above 0.1 g. 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 blastfurnace 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. ”
Laboratory staff undergo biosafety training on
sampling collection procedures at the waste
discharge area of a rural hospital
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 slump to 130 mm for slanted sections to avoid concrete sliding off shuttering.
Sheldon Temlett, contracts manager at M&D Construction, highlights the importance of this mix performance. “With such dense steel and complex geometry, AfriSam’s mix gave us the workability we needed without compromising quality. Their team worked closely with us to adjust slump levels and plan deliveries around our 12 m³/hour pour rate.”
AfriSam territory manager Toni Williams adds that logistics were carefully aligned with construction progress to avoid delays or idle time on site.
“Coordination was key to supporting M&D’s controlled rise rate of one metre per hour, especially as the concrete had to partially set before each formwork lift could proceed.”
Construction of the Main Reef water tower began in September 2024 and is scheduled for completion in April 2026. Once commissioned, it will provide essential water infrastructure to approximately 20 000 homes in the Goudrand housing development – a major project spearheaded by the Gauteng Department of Housing, the City of Johannesburg and Blue Print Housing.
