AfriSam recycles concrete in its sustainability drive
Readymix concrete that is returned to the supplier for various reasons has in the past created an environmental headache, but AfriSam is now able to recycle this material for road-building purposes.
While readymix suppliers must always be prepared to accommodate a certain portion of returned concrete from site when the construction schedule does not go according to plan, for instance, disposal of this material can create challenges. So, in line with its commitment to recycling in its Environmental Management Programme, AfriSam has over the years used various strategies to deal responsibly with returned concrete.
A breakthrough was made when the management team at AfriSam’s Jukskei Quarry in Midrand, Gauteng, experimented with including recycled concrete in the G5 sub-base product required for road-building. Standards permit this grade of product to comprise material from more than one source. They also require that it contain about 80% fines content which the recycled concrete was well-suited to deliver.
As a result, some 15 to 20% of the G5 product can be made up of recycled concrete, giving a good mixture of decomposed material and returned concrete. Quality remains key, and AfriSam ensures that all its products comply with the COLTO (Committee of Land Transport Officials) material grading specifications from the South African Bureau of Standards.
AfriSam’s G5 sub-base with recycled concrete was first used on the N1 highway extension work around Johannesburg – part of the Gauteng Freeway Improvement Project – and the contractor was well satisfied with it. Since then, its success has been replicated in a range of other projects.
The recycling process begins when the returned concrete is contained in a dedicated area of the readymix site and allowed to dry. Using a hydraulic hammer mounted on an excavator, the dry returns are broken up into chunks of 250 to 400 mm in size. After being hauled to a secondary stockpile, the material is checked and blended by plant operators before being fed into a jaw crusher.
Load-haul operators also play a role in checking that the material is within specification, and must be selective in what they bring to the stockpile to ensure blending of the appropriate quantities before crushing. Crushed material is then homogenised and stockpiled ready for use.
This innovative solution also has positive spin-offs for the readymix site itself. As there is no slush around the plant, there is less potential for contamination and a smaller carbon footprint is created. It should be remembered that no public dumping facilities would accept concrete in these quantities, making these strategic responses even more vital.
In addition to its environmental benefits, the recycling process ensures sustainability by creating a revenue stream for the recycled material; its inclusion in a saleable, quality G5 product means that it is helping offset the costs that returned concrete places on the business.