OPS revises standard to allow recycled concrete
In 2014, the Canadian Standards Association amended its concrete materials standard (A23.1) to allow the use of reclaimed concrete material as an aggregate in unshrinkable backfill. At the request of Aggregate Recycling Ontario, the Ontario Provincial Standards for Roads and Public Works (OPS) has now revised its municipal-oriented standard for unshrinkable fill (OPSS.MUNI 1359) to allow the use of recycled concrete.
“Cities and towns across Ontario frequently have to cut trenches into existing roads and streets to install or repair utilities,” says Brian Messerschmidt, executive director of the Aggregate Recycling Ontario. “Upon completion, the pavement must be restored. An alternative to backfilling these trenches with unbound granular aggregates, is the use of unshrinkable backfill, also known as flowable fill or Controlled LowStrength Material (CLSM).”
Unlike granular backfill, which must be compacted, unshrinkable backfill is capable of flowing to fill excavation voids and helps to eliminate future settlement of the trench material. Unshrinkable fill is delivered by ready-mix trucks and like other concrete, the mixture includes cement, aggregates and water. The amount of cement used is considerably lower to achieve a low strength so that the backfill can be readily removed if required in the future.
That standard was one of many revised standards recently published in November 2016 and is available from the OPS website.
“Aggregate Recycling Ontario wishes to thank the OPS volunteers who created this revised specification and saw the wisdom of a specification change that contributes to sustainable resource management,” said Messerschmidt. “This is a good news story. It didn’t make sense to continue to specify the highest quality concrete-quality stone for this product. Every tonne of recycled aggregate used, is one less tonne of primary aggregate required from a pit or quarry.”
Aggregate Recycling Ontario has also requested that the OPS revise OPSS 1010 (granular base and sub-base aggregates) to allow the use of recycled aggregate in granular B, type II products. The current 2013 specification, however, is not up for review until 2018 (five-year cycle).
Aggregate Recycling Ontario was established in July 2011 to provide a unified platform for industry stakeholders that recover, recycle and consume aggregate materials in Ontario. Initiated by the Ontario Stone, Sand & Gravel Association and the Toronto and Area Road Builders Association, the organization was formed to bring attention and find a solution to the province’s growing piles of reclaimed concrete and asphalt, as well as expand the opportunities for recycling aggregates. Processed properly, recycled aggregates can meet performance requirements and offer a suitable alternative to primary aggregates.