Construction leader AfriSam has conducted two large continuous pours as part of its readymix supply to WBHO Roads and Earthworks’ contract at Watt Street Bus Rapid Transport (BRT) station in Wynberg, Johannesburg.
The two pours – conducted in February and June this year – comprised over 550 m3 each, according to AfriSam’s key accounts manager, Randal Chetty. The concrete work on the BRT project included piles, pile-caps and bridge structures including precast concrete beams.
Daniel Kwele, construction manager at WBHO Roads and Earthworks, says the contract involved extensive earthworks to excavate the underground station, and almost 9,000 m3 of readymix for concrete works.
“The southern portion of the main bridge over Pretoria Main Road included the installation of 342 lateral support piles and pile caps to carry about 244 precast concrete beams,” says Kwele. “To the north of the bus station, the most notable structures are the twin viaduct bridges, resting on 220 end-bearing piles and over 70 footings.”
He notes that the close collaboration with AfriSam and detailed planning for the continuous pours helped to foresee and mitigate any challenges. “The pours became a smooth process, thanks to the commitment from AfriSam’s senior management,” he says.
Kevin Naidoo, operations manager for AfriSam’s central plants, notes that in large pours for this kind of application, the window period for pumping and placing the high-spec concrete tends to be limited – due mainly to the high cement content in the mix.
“This meant that we had to have fresh concrete on site all the time, with no queueing of trucks,” says Naidoo. “The laboratory at our Jukskei plant – close to the project – also assisted with checking the quality of our 150-slump mix.”
Readymix was supplied from AfriSam’s Wynberg plant, with 14 to 17 trucks dedicated to supply WBHO’s concrete pumps during the large pours. Chetty says that AfriSam is one of only a few concrete suppliers with the capacity to conduct the size of pours required for this contract, within the timeframe required.
“This was also a highly-specified project in terms of concrete mix designs, requiring considerable upfront collaboration with the engineers to approve the designs within the SANRAL specifications,” he says.