Civil Engineering September 2022 | Vol 30 No 8

6 September 2022 Civil Engineering “This took the civils work on the northbound side of the bridge to about 80% completion. Civils work on the south- bound side is also well advanced in terms of wing wall demolition and beginning the lateral support,” he says. The more substantial task will be the Lynnfield Bridge, where the highway crosses the R103 provincial road. The reconstruc- tion will first need the existing structure to be demolished completely in two phases. “The bridge section over the north- bound highway will be demolished first, after traffic is diverted onto the contraflow lanes on the southbound side. The demolition will be followed by the construction of new abutments, which will both widen and lengthen the struc- ture. Here, the concrete requirement will be 1 500 m 3 ,” says Eagleton. At both bridges, prestressed beams will be laid across the abutments. While Lynnfield has one centre pier, Mpushini has two abutments with no pier. A spe- cialist subcontractor will produce these precast beams. Another precast element will be permanent shutters between the beams, which will also be supplied by a precast manufacturer. The design of the Lynnfield bridge includes a precast side panel on either side of the bridge deck, adds Eagleton. This is to facilitate a slight cantilever, which is not possible to cast in situ with traffic moving below on the R103. “Existing on-ramps and off-ramps will be upgraded, not only to make them wider but to lower the ramp levels to tie in with the lowering of the R103 road. Where the R103 passes under Lynnfield Bridge, there will therefore be more height to allow pas- sage for larger trucks,” he says. DEMANDING STANDARDS Robinson emphasises the high construc- tion standards being applied on this contract, which also place stringent demands on the materials being supplied by AfriSam. These standards relate to a range of aspects, from the crushing specification of aggregate material to the durability requirements of concrete. He notes that the mix design for the CRCP layer is one of the most technical and advanced designs that Rumdel has encountered. “This requires partners who can reli- ably meet these exacting standards and conduct the necessary testing,” he says. “With AfriSam’s experience and technical capability, they are able to do this.” Once the concrete mixes have been approved, independent in-situ testing will have to be conducted on a 100 m 3 trial section of the roadway’s reinforced concrete layer. Chetty points out the high volumes of readymix that AfriSam will be required to provide when the CRCP layer is poured. The project will use 150 m 3 per shift, with two shifts in each 24-hour period – for six days a week. “Our planning for this will be critical, and will require long hours and reliability across our operations and supply chain,” he says. Eagleton notes in conclusion that the work related to placing of concrete for the CRCP layer will be conducted through labour enhancing methods. “This means that after AfriSam delivers the readymix by truck, the placement and levelling will be done by hand – rather than using a paver. This will generate more employ- ment in the area,” he says. To ensure adequate human resources for this sizeable project, Rumdel has de- ployed a management and support team of 24 staff. The total number of people on the contract was already over 340 by mid-2022, which included 16 contractors targeted in terms of contract participation goals (CPG) and four domestic contractors. For more information www.afrisam.co.za @AfriSamSA @AfriSam AfriSam Two large concrete retaining walls are nearing completion Two major bridges, Mpushini and Lynnfield, will also be revamped