Recycling concrete a key piece of circular economy: workshop
The reuse of crushed concrete is increasingly important to sustainable resource management, reducing greenhouse gas emissions and the move toward a circular economy, a national workshop on the issue heard February 10.
The workshop, sponsored by two industry companies in Ontario, was presented by the Circular Innovation Council of Canada and Circular Economy Leadership Canada, non-profit groups advocating waste reduction and reuse. Some 90 individuals from across Canada participated.
The goal of the workshop was to look at experience with and barriers to the reuse of recycled concrete aggregates in jurisdictions across Canada. In Winnipeg, RCA has been used in road construction and renewal for about 20 years but the adoption of new roadbuilding specifications has triggered a review of the practice.
The participants heard that minimal use of RCAs is made in roadbuilding or otherwise. For example, in Ontario RCA makes up less than 7% of the 180 tonnes of aggregates used annually.
Municipalities are the largest consumers of aggregates, using 60-70 million tonnes per year. Jo-Ann St. Godard, executive director of the Circular Innovation Council, said that municipalities are responsible for 80% of public procurement, accounting for the expenditure of $160 billion each year in Canada.
This is where the value proposition sits, in particular with public works construction, St. Godard said.
Officials with the City of Toronto explained the work done since 2013 in that city to respond to concerns that, from observed performance, RCAs were not performing equivalently to virgin aggregates in roadbuilding.
Sampling and testing were done of stockpile materials, specifications were updated and municipal staff were trained in how to inspect recycled aggregates and asphalt materials. Inspection and testing of materials at suppliers of recycled concrete found that the stockpiles were good in quality.
Toronto has decided to use recycled concrete in roadbuilding but not in trenches.
The benefits of reusing crushed concrete that is pulled up from roads and water-renewal projects include:
- reducing the draw from virgin aggregate resources (extending the life of pits and quarries);
- cutting the concrete waste going to landfills;
- alleviating the GHGs produced in transporting aggregates; and,
- meeting the goals of environmental targets, including for recycling and the carbon footprint.
However, the challenges and the risks at present in Canada include:
- Consistency in quality of delivered material
- Ensuring short-term and long-term performance of the road long-term
- Prescriptive nature of roadbuilding specifications written by municipalities/provinces
- Perceived risk in allowing use of RCAs – many jurisdictions are not familiar with RCAs or have had negative experiences in the past.
Academic researchers told the workshop there is work to be done to improve the characteristics of aggregates from recycled concrete, but that they are in wide use – sometimes mandated – in jurisdictions in areas of the world where aggregates are less available and carbon-footprint concerns are a priority.
Comments included:
- there is good take-up of recycled concrete in roadbuilding in Europe
- Canada is using up its virgin aggregate resources – four billion tonnes have been used in 25 years.
- Aggregates are a component of concrete, and we need to review where were using them. Some 75% of all concrete used globally is used in non-structural infrastructure, which is unnecessary.
