Construction World July 2024

Concrete is a central component of the Willowton Group’s expansion of its Isando plant.

The project includes a large 30 m by 90 m bunker with 11.5 m high walls, topped with a 5 m steel structure.

vertical joints in the wall, which aims to reduce the risk of water seepage and corrosion. The concrete bases comprised a circular footing with a 2,2 m wall of 600 mm thickness. A conveyor channel runs through the middle of the structure. Van der Westhuizen says he was pleased to be able to rely on AfriSam, who consistently delivered a high quality product – with the 35 MPa mix regularly reaching 45 MPa strengths. Among the challenges, he points out, was that the water table was relatively close to surface – just 2,5 m below natural ground level. In terms of concrete admixtures, this factor affected the choice of mix for the cleaning tower, as well as a for a 7,5 m deep lift pit. “The high water table, as well as the summer rains, meant that we had to continuously pump water from the site,” he says. “With the amount of groundwater present around the completed construction, we decided to use a waterproofing admixture in the concrete as an added precaution.” Space on the site was confined, especially as an existing hardstand had to be demolished, crushed and stored as a 4 500 m 3 stockpile of G5 fill. Excavating to depths of 7,5 m

had to be done in stages, extending well beyond the concrete footprint. Apart from the bunker, most of the concrete could be pumped using a 35 m capacity boom pump to accommodate space limitations.  The concrete work also included the bases for four silos, using a total of 700 m 3 of concrete.

The total concrete volume for constructing the bunker was approximately 1 500 m 3 .

17 CONSTRUCTION WORLD JULY 2024