Aggregate Harvest

New processing methods economically recover C33-grade material from construction, demolition and excavation waste streams

The CDE washing technology arms Calgary Aggregate Recycling to process 250 tons per hour of construction and demolition waste material, transforming it into a high value suite of construction products, including: 0-1mm fine and 0-4mm coarse sands, plus 4-10mm undersize, 10-20mm midsize and 20-40mm, 40-100mm and >100mm oversize aggregates. The technology yields material matching or on the cusp of ASTM C33-level purity. Calgary Aggregate Recycling summarizes operational details in four steps: Monitoring of each load arriving at the yard; mechanical processing of all contaminated soil and material; using recycled water for soil or material treatment and sand & gravel capture; and, separating contaminated from clean materials.

One of the newest instances of circular economy principles impacting concrete materials is recovery of sand & gravel from inert or contaminated soils tied to construction, demolition and excavation. Investors in next generation wash and classification plants aim to tackle new transportation and environmental economics forcing pursuit of alternatives to traditional landfill solutions for aggregate-bearing waste.

Calgary Aggregate Recycling (CAR) in Alberta is among the latest operators to open a plant equipped with advanced washing, screening, classifying and separating technology from CDE, which coined “Dirt to Dollars” as a 2023 ConExpo-Con/Agg motto. CAR modeled its operation after CDE-equipped peers Posillico Materials, New York and Repurpose Aggregates, Maryland. Their investments coincide with state, province or local agency measures or incentives addressing inert or contaminated soils. Such waste streams are rooted in industrial brownfield redevelopment, replacement of obsolete buildings or homes on their original sites, along with environmental, transportation or utility infrastructure upgrades or reconfiguration. Disposal of aggregate-bearing soils has become increasingly expensive due to a) greater transfer distances to landfills charging higher tipping fees, and b) volatile trucking costs reflecting higher fuel prices and driver wages.

Prior to enlisting CDE for a wash and classification plant, dedicated in mid-2023, CAR lacked an outlet for contaminated soils. Fully loaded dump trucks were routinely dispatched to a landfill licensed for such materials. The diesel consumption attending the 350-kilometer round trip for loads proved sufficient to garner the attention of Emissions Reduction Alberta, an agency that assists companies or organizations eyeing capital expenditures ultimately lowering the Province’s carbon dioxide output.

“We set out to establish economical and viable solutions to position Alberta as a leader in sustainable and responsible construction,” says CAR President Travis Powell. “We started this process by applying for a grant with Emissions Reduction Alberta. It believed in the impact our proposal could have and gave us the start we needed to get to where we are today. With the ERA’s backing and CDE’s expertise and proven experience in this space, we are strongly positioned to make significant strides in our mission to reduce the cost of construction—socially, environmentally and economically.”