Civil Engineering September 2022 | Vol 30 No 8

Civil Engineering September 2022 5 of lean mix concrete, on top of a stabilised layer which uses AfriSam’s Roadstab ce- ment,” Robinson explains. Roadstab is a specially engineered composite cement used specifically in road stabilisation, ensuring uniform distribution of the stabilising agent throughout the stabilised layer. Around 3 300 tonnes of cement will be required in all. By June 2022, AfriSam had supplied about 200 tonnes of Roadstab. The G5 material for this sub-base layer is being supplied from AfriSam’s Pietermaritzburg quarry, while the G6 and G7 material for fill layers, as well as blasted rock for undercut sections, comes from Umlaas Road. Chetty highlights the scale of the project and the high volume of aggregates which it will consume. To maintain AfriSam’s contribution, the Umlaas Road operation is running at full steam. “AfriSam has done everything they can to accommodate our construction material requirements within our time and other constraints,” says Robinson. The company will be able to meet Rumdel’s demand for readymix and for the coarser aggregates. SOLID PROGRESS Progress on phase one – the temporary widening of the southbound carriageway – has been good, with two large concrete retaining walls and two mechanically sta- bilised earth walls nearing completion. By June 2022, this phase was over 80% com- pleted. Phase two, which is the reconstruc- tion of the northbound carriageway, began in August 2022. This work will continue until May 2023. The third phase, to fully reconstruct the southbound carriageway, will be underway until January 2024. “In phases two and three, we will be recycling the jointed concrete pavements. Working with AfriSam, we are planning to use this recycled concrete in the ‘inter- layer’ – one of the lower layers beneath the concrete pavement,” says Robinson. It is expected that between 60% and 80% of the road layers for the new highways will be recovered from the existing layers. He adds, “Rumdel shares the vision of our client that we re-use and upscale as much construction material as we can. While the sheer volume of material in a project of this size does create a challenge when it comes to stockpiling, recycling represents an important saving to the tax- payer and reduces our carbon footprint.” He adds that Rumdel generates sustainability reports for the client regu- larly over the duration of the contract, detailing how it is managing and reducing its carbon emissions. BRIDGE RECONSTRUCTION The two major structures on this stretch of highway are the Lynnfield Bridge and the Mpushini Bridge. “We will be widening the Mpushini Bridge – where the highway crosses the Mpushini River – in a process that entails casting of new abutments and placing of beams across the deck. The old deck will be demolished, and the new deck constructed to the new widened position,” explains Rumdel site agent Kevin Eagleton. This work will require 1 200 m 3 of concrete, and will be carried out in two phases, in line with the necessary traffic accommodation on the carriageway. By mid-2022, widening work was already underway. Excavations had been done and lateral support provided to the structure; the wing walls had also been demolished. To date, AfriSam has supplied some 4 000 m 3 of 35 MPa concrete Around 3 300 tonnes of AfriSam Roadstab cement will be used for road stabilisation