Recycled concrete could be a sustainable way to keep rubble away from landfills

The results of a new five-year study on recycled concrete show that it performs even, and in many cases even better, than conventional concrete.

Researchers from UBC Okanagan’s School of Engineering conducted side-by-side comparisons of recycled and conventional concrete under two common applications: a building foundation and a municipal sidewalk. They found that the recycled concrete had comparable strength and durability after five years of service.

“We live in a world where we are constantly looking for sustainable solutions that remove waste from our landfills,” says Shahria Alam, co-director of UBC’s Green Construction Research and Training Center and principal investigator on the study. “A number of countries around the world have already standardized the use of recycled concrete in structural applications and we hope our findings will help Canada follow suit.”

Construction and demolition waste materials contribute up to 40 percent of the world’s waste, according to Alam, and in Canada waste amounts to nine million tons per year.

Researchers tested the compressive strength and durability of the recycled concrete compared to conventional concrete.

Concrete is typically composed of fine or coarse aggregates which are bonded together with an adhesive paste. Recycled concrete replaces the natural aggregate for the production of new concrete.

“The composition of the recycled concrete gives that product additional flexibility and adaptability,” says Alam. “In general, recycled concrete can be used in retaining walls, streets and sidewalks, but we are seeing a shift towards its increased use in structures.”

As part of the findings, the researchers found the long-term performance of the recycled concrete adequately compared to its conventional form and found no problems over the five years of the study. Indeed, recycled concrete had a higher compressive strength rate after 28 days of curing, while maintaining greater or equal strength during the research period.

Researchers suggest that recycled concrete can be a 100% replacement for non-structural applications.

“As innovations continue in the composition of recycled concrete, we can imagine a time in the future when recycled concrete can be a substitute even within more structural applications.”