AfriSam’s Jukskei quarry in Midrand has cracked the problem of returned concrete with an environmentally-friendly solution that even pays its own way.

Every provider of readymix concrete must expect a certain amount of returned material as a result of unforeseen circumstances on the construction site for which it is destined. Production superintendent at Jukskei Quarry, Mohamed Docrat, finally found a sustainable solution: to re-use the concrete in the company’s G5 sub-base product for road building.

“Also, the process of breaking up the returned concrete generates plenty of fines, which is beneficial to the product as the class specification for G5 demands that it must comprise about 80% fines,” he adds.

A suitable process was devised and tested, in which an excavator-mounted hydraulic hammer breaks up the dry returns into 250 to 400 mm sizes, after which it is loaded by excavator into a dump truck and hauled to a secondary stockpile. The plant operators check that the material is within specification, and the blended material is then fed into a jaw crusher.

The crushed material goes onto a production stockpile where it is homogenised, and it is taken by dump truck to a set-back stockpile where it is ready for sale.

Between 15% and 20% of recycled concrete is added into the G5, according to Mohamd. “This gives us a good mixture of decomposed material and returned concrete,” he says. “During our G5 run to produce the material for sub-base layers in roads, we began testing by trickle-feeding a small portion of returned material into the G5, and found that it worked well.”

This environmentally-friendly solution also means no slush around the Jukskei Quarry plant, less potential for contamination, and a smaller carbon footprint.

Afrisam, Maxine Nel

Tel: (011) 670-5893