COVER STORY
AfriSam concrete expertise for WBHO’s BRT contract As contractor WBHO Roads and Earthworks makes good progress on the bus rapid transit (BRT) station at Watt Street in Wynberg, Johannesburg, it is being well supported with almost 9 000 m3 of readymix concrete by construction materials leader AfriSam.
AfriSam dedicated between 14 to 17 trucks to the job of servicing WBHO’s concrete pumps during the large continuous pours of around 550 m3 each. AfriSam has extensive experience in achieving special mixes and ensuring reliable concrete supply for major bridge works
T
he underground BRT station at the Watt Street interchange is part of the City of Johannesburg’s Rea Vaya system to integrate and improve public transport facilities. The Watt Street station will serve the Rea Vaya bus route from Sandton to Alexandra, as well as from Parktown to Alexandra. The project is driven by the Johannesburg Development Agency. According to Daniel Kwele, construction manager at WBHO Roads and Earthworks – a division of WBHO Construction – the early work from July 2018 included the demolition of the existing Watt Street bridge and the relocation of telecommunication and other existing services. “The earthworks for this project were substantial, involving over 100 000 m3 of material being moved,” says Kwele. “To limit our impact on the traffic pressure in the area, we moved most of this volume at night while concentrating on concrete structures during the day.” The earthworks allow for the bus lanes to descend between reinforced earth walls
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IMIESA October 2020
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
into the underground station, above which a new interchange is constructed for mixed traffic. The first concrete work included the installation of 342 lateral support piles on the southern portion of the main bridge over Pretoria Main Road, each with pile caps on which would rest 244 precast concrete beams. This section of the project also included installing 18 km of ground anchors, 10 km of soil nails and 13 000 m2 of shotcrete. A spine beam in the midsection is fixed on one end and supports the 37 t beams all the way on to the northern bridge section. “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 says. “The bridges required two very large continuous concrete pours – one in February 2020 and another in June 2020.” Further north are four reinforced earth walls to allow for the mixed lanes to tie back from Chadwick Street into Pretoria Main Road.
Planning and teamwork Randal Chetty, key accounts manager, AfriSam, highlights how the experience from previous contracts with WBHO helped to strengthen the working relationship. “Our pre-contract meeting created a good foundation for everyone to know what’s expected, and from there the schedules were generated for the deliveries of the concrete itself,” says Chetty. “The big continuous pours in particular demand a huge amount of planning, so it was vital that everyone worked together to make these successful.” The site is located just a kilometre from the AfriSam Wynberg readymix plant, and AfriSam dedicated between 14 to 17 trucks to the job of servicing WBHO’s concrete pumps during the large continuous pours of around 550 m3 each.
Expert mix formulation and delivery “This was a highly specified project in terms of concrete mix designs, requiring considerable upfront collaboration with the engineers to approve the designs within the
