Construction World October 2017

to an average depth of about 10 m, and socketed into bedrock,” he says. Making up the 12 spans between the piers are 60 concrete I-beams, each measuring 26 metres with a zero angle of skew, a straight horizontal alignment and a flat vertical alignment. These are placed on elastomeric bearings on top of the piers. “Through careful planning and detailed consideration of load requirements, we are able to use mobile cranes on the bridge itself to lift and place the I-beams,” says Douglas. “This allows a cost effective solution in place of having to employ much larger cranes with greater reach from the bottom of the bridge.” The final stages of the contract will involve the refurbishment of the road itself, where 2 200 m 3 of stabilised sub base will be laid down as well as 2 000 m 3 of crusher run base. In finishing 13 500 m 3 of Cape Seal with 8 000 m 2 of asphalt between 30 mm and 40 mm thick. Douglas highlights the company’s focus on safety alongside quality, which allowed the project to pass the landmark of almost 155 000 Lost Time Injury Free (LTIF) hours by mid-2017. “At Botes & Kennedy Manyano, we have a certain way of doing things, and we like to grow our employees into a mature and professional culture where they prize both the quality of what they do, and the safe practices that underlie our strategy of zero- harm,” he says. “Our project team on the Hopetown bridges embodies this ethos, and they have shown their commitment in the smooth implementation of this important contract. For Botes & Kennedy Manyano it is about building something real.”  Once all the minimum contract specifications had been met, AfriSam would run final mixes, conduct durability index testing for reporting and submit this to the SANRAL consulting engineer for sign-off.

AfriSam designed a range of concrete mixes for the project to ensure optimal durability and to meet certain workability or slump requirements.

SANRAL’s specification of a performance- based concrete – rather than providing a prescriptive specification – put the ball in the court of the concrete designer.

AfriSam’s Ulco factory near Barkley West in the Northern Cape and batched with locally sourced aggregates and sands. In total, about 28 000 bags of cement made the 200 kilometre trip from factory to site. For optimal mix designs, AfriSam collected and analysed samples of ma- terials to be used for the concrete from site, running trial mixes at its SANAS- accredited laboratories in Roodepoort. “Once all the minimum contract specifications had been met, we could run final mixes, conduct durability index testing for reporting and submit this on the SANRAL D2 form for the consulting engineer to sign off,” says Croney. “Once these were approved, the contractor could conduct site trials, which were tested at the site laboratory, to measure conformance and performance against the AfriSam CPE laboratory mix designs.” Another indication of the scale of these concrete works was the fact that almost 9 700 m 3 of formwork was used. Of the 11 new piers to be built, nine had been completed by August 2017. New abutments on the north and south banks of the river were also built, requiring considerable earthworks, says Van Tonder. “Over a dozen 750 mm diameter piles were drilled at each abutment, down

In total, AfriSam supplied 28 000 50 kg bags of High Strength Cement from its Ulco plant, 200 kilometres from the site.

a final 1,5 metre lift. Concrete was poured from the causeway utilising a crane and concrete buckets.” The project’s concrete Concrete for the project was produced at the contractor’s efficient Karoo-style batching plant close to site, where AfriSam’s High Strength Cement – its CEM II A-M (L) 52.5N product – was delivered in 50 kg bags from

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CONSTRUCTION WORLD OCTOBER 2017