South African aggregate producers are drawing up plans to formalise the aggregate recycling industry to ensure that previously used materials are given new life in the best possible manner.
The aggregate producers’ organisation Aggregate and Sand Producers Association of Southern Africa (Aspasa) held a workshop on aggregate recycling earlier this year, where Aspasa director Nico Pienaar stated that the recycling of aggregates will become an important means of reducing the environmental impact of quarrying and construction.
He added that, as resources become more scarce in built-up areas, the use of recycled aggregates could provide an important means of offsetting rising transport costs that will be incurred during the transport of virgin aggregates into the cities.
Pienaar explained that aggregates are the most mined minerals in the world and are usually produced to set standards, which determine their suitability for a range of applications, normally within construction. “As such, demand is driven by building professionals’ requirements for materials that are based on concrete mixes, road surfaces, railway ballast or decorative purposes.”
He noted that aggregates in their virgin state are of the purest quality and have known characteristics. However, when recycled, the aggregates used in building materials are altered with the addition of concrete, fines and chemicals. Pienaar suggested that a classification –based on reliable data and statistics – of recycled aggregates needs to be obtained to encourage the best possible use of recycled aggregates in the most appropriate application.
“Therefore, for it to become a viable product, we need to establish and implement quality control procedure wherein we can establish that the recycled material can be used in exactly the same way as a non-waste, that it can be stored and used with no worse environmental effects than the material it is intended to replace, and that it conforms to the same specification as aggregate products,” Pienaar explained.
He added that, while building rubble has been used for centuries as backfill, this need not be its only application in the construction industry. International experience shows that this waste can also be used in road building and other types of construction where mixed materials are being found to be suitable, “if they are properly classified”.
He noted that as the industry establishes itself, issues like identification, classification and uses of recycled materials are still being debated and determined.
Pienaar stressed that the main determination of whether recycled materials are viable lies within a regions’ supply chain and logistics infrastructure, as costs associated with handling and transport will ultimately determine whether recycling makes economic sense.
In the meantime, positive interventions are already taking place across the country with a working committee already formed in the Western Cape, and best practice being compiled for the inclusion of secondary materials in road layers and how and when to substitute virgin materials. Concrete specifications are also being examined to include the use of recycled materials and the effect on durability.
Pienaar noted that guidelines are also being put in place to assist recyclers in working within the parameters of legislation and best practices as dictated by various professional bodies within the construction industry.
These guidelines include: applicability of legislation and legal requirements, best practice sourcing and separation at source, best practice crushing and screening, best practice stockpiling/blending of crushed materials, material specifications for use in roads, material specifications for use as concrete aggregates, and best practice design, construction and quality control.
“Globally, the trend is towards recycling to make better use of our available resources. Despite South Africa’s abundant mineral wealth, it is foreseeable that aggregates may become more difficult to obtain and will [therefore] need to be shipped from further afield. “
He concluded that recycled aggregates will play an important role in offsetting the rising price of virgin aggregates because of the associated transport and handling costs. As a result, companies and municipalities should think twice about relegating all building waste to landfill sites, Pienaar noted.
Aspasa is a voluntary membership, private sector producers association, as well as a member (but still autonomous structure) of the South African Chamber of Mines. However, it represents those companies that are in the business of producing aggregate and sand and is better known for operating quarries, sand pits and crushing operations.