Rock replay: Processing C&D materials

By |  May 7, 2015

An Ontario company realizes important environmental goals, customer satisfaction and higher profits by processing C&D materials.

Extending the life of its limestone quarry, engaging in environmental sustainability and providing a cost-effective aggregate product to customers are among the benefits Ontario’s Nelson Aggregate Co. sees in recycling asphalt and concrete materials.

An aggregate mining and construction materials supply company, Nelson Aggregate has been in partnership with Lafarge Canada Inc. and Steed and Evans Holdings Inc. since 1983. The company is engaged in extraction, processing and distribution of crushed limestone, sand and gravel, and asphalt products, and the company’s locations include operations in central and southern Ontario, as well as the Niagara region.

Reclaiming product

“We’re a mid-size aggregate producer that provides plus or minus 3 million tons of aggregate each year,” says Steve Drew, quarry manager. “We began recycling concrete and asphalt and blending them with our limestone products in the late 1980s. We started with a hollow core, pre-stressed concrete product that was leftover finished product from a customer we used to supply.”

Nelson Aggregate customers reap the greatest cost savings from the company’s recycling activities because they can purchase aggregate products at lower prices. An added economic benefit for Nelson Aggregate is the decreased cost of mining virgin limestone, which includes savings on drilling and blasting, hauling, equipment maintenance and product processing.

“Blending the recycled material also extends the life of our quarries,” Drew says. “We still see our greatest demand coming from the private sector. From an environmental viewpoint, recycling is the right thing to do. It keeps all this material out of landfills and stockpiles where it would sit for decades. Our customers appreciate the environmental aspect of the products. We see a growing governmental emphasis on recycling aggregate products, too. From a corporate consciousness standpoint, recycling is an important company activity.”

Added benefits

In addition to recovering some demolition and transportation costs, construction companies that sell recyclable products to Nelson Aggregate recognize the advantages of engaging in environmental sustainability. They are also relieved of having to find a landfill that will accept deposit of their demolition material.

“Some landfills no longer accept recycled asphalt or concrete,” Drew says. “The cost of disposing of it can become significant if a company has to haul it too far. Most landfills just won’t take it and, if they do, tipping fees are very expensive here.”

Nelson Aggregate has moved into not only concrete recycling but also asphalt recycling. Materials come from rebuilt roads and buildings. In 2014, the company recycled more than 200,000 tons of material.

“Concrete is a smaller portion of what we’re doing at the moment but that could change year to year,” Drew says. “Our recycled asphalt stone blend is typically 25 percent to 30 percent recycled product and 70 percent to 75 percent virgin limestone. In 2014 we increased our use of recycled asphalt from 70,000 to 75,000 tons of RSA that went back into the marketplace.”

Inspecting quality

The properties and quality of recycled asphalt pavement (RAP) can vary greatly, depending on the properties of the original materials used to create the mix. Quality can also be affected by the number of times a paved road was resurfaced, crack sealed and patched or seal coated.

While the majority of its RAP and recycled concrete products are sold to the private sector, Nelson Aggregate developed a detailed inspection protocol to ensure they purchase 100 percent recyclable products.

Because excess granular material, soil or debris can sometimes become mixed with stockpiles of broken asphalt or concrete, inspection includes checking for the presence of these unacceptable materials.

Demolition approaches – such as milling or crushing recyclable pavement – can also affect material quality. Inspection of a load verifies particle size and degradation. Most sources are likely to be well-graded coarse aggregate, perhaps slightly finer than crushed natural aggregates. Due to weathering, cement adhering to aggregate is typically harder than new asphalt cement. Moisture content also varies.

Acquiring recyclable materials

Nelson Aggregate’s largest recycling company is in Burlington, Ontario, about 30 minutes west of Toronto. The location is good for customers bringing in broken asphalt or concrete. Often, customers bringing recyclable products in are also using Nelson Aggregate products for new road or building projects. Most of the product Nelson Aggregate purchases comes from a 75-mile region.

“We receive material all year round but we make it clear that we’re not a dump or fill site,” Drew says. “Every load that comes into the site is inspected to ensure it doesn’t contain unwanted material. We don’t accept materials mixed with anything else. If it’s asphalt, the entire load must be asphalt, and the same with concrete. We’ve run into issues in the past, which led to development of our current stringent protocol. Every load that comes in is inspected by our personnel to make sure it’s acceptable. If it isn’t, it’s turned away.”

Reprocessing procedure

Because they cannot process both recyclable material and virgin limestone at the same time, Drew’s company has found it to be more economically feasible to hire a contractor to crush and handle recycled material. They maintain a separate site for receiving and processing recycled product.

“Most of the demand for our recycled blends is coming from the private sector,” Drew says. “The public sector is still somewhat leery of using blended products, especially with regard to recycled asphalt. In infrastructure projects, which typically require high-quality base material, industry experts aren’t convinced of the quality of blended products.”

Selling blended material

Studies on the efficacy of recycled asphalt and cement products combined with virgin aggregate such as limestone have been conducted since the first “reclaimed asphalt” projects were undertaken in the 1970s. While some studies indicate that blended aggregate products contain necessary base material qualities, American asphalt pavement and concrete industry experts haven’t fully embraced the products.

In a recent test of blended aggregate quality, John Dingeldein, vice president of Soils & Materials Engineers in Kirtland, Ohio, worked with Kurtz Bros. Inc. of Independence, Ohio, to compare performance of unbound base course containing a blend of recycled concrete aggregate and foundry sand with a control base course of virgin limestone. The project was partially funded through a competitive Solid Waste Management Assistance grant from the U. S. Environmental Protection Agency (EPA).

The blend of recycled concrete aggregate and foundry sand met the Ohio Department of Transportation’s (ODOT) 304 Aggregate Base Specification. At the completion of the study, the blended product was deemed to have performed as well as, if not better, than the virgin limestone product.

“The road project was in Cuyahoga Heights,” Dingeldein says. “The city allowed us to do 50-ft.-long test sections using different aggregates. Our control section was straight ODOT 304 crushed limestone. The next 50 ft. was a section using predominantly recycled concrete with about 16 percent foundry sand. A third section was blended with construction demolition debris that had been crushed down to a 304 aggregate.”

In the project, the same base course thickness was used throughout the road project. Once the road was completed, a heavyweight deflectometer was used to send shockwaves through the deflectometer foot that traveled into the subgrade. Deflectometer sensors recorded the shock wave data so Dingeldein and the research team could compare subgrade modulates for each 50-ft. section.

“We found that the recycled concrete and demolition debris material was equivalent or even bit better than the straight limestone section,” Dingeldein says. “I believe with recycled concrete materials there’s some extra benefit from having freshly crushed material that re-exposes fresh material, which cements better so you get a stronger base material compared to straight 304 limestone.”

Recycling growth

According to the National Asphalt Pavement Association, the EPA and Federal Highway Administration identified RAP as America’s number-one recycled product as early as 1993. In 2013, RAP usage reached about 67.8 million tons, a 21 percent increase from 2009. More than 99 percent of asphalt reclaimed from roads and parking lots was used in new pavement.

Dingeldein says Virginia and North and South Carolina DOTs have used recycled products in their projects. In Virginia’s case, there’s no mention of recycled concrete aggregate (RCA) in their state strategic plan, however, it is approved for use in state projects.

“Often, when a state uses RCA, they’re recycling miles of it and set up a processing plant right on the road site,” Dingeldein says. “Wisconsin is one state that’s done this for a long time. If nothing else, RCA is often used in the base course.

“In Cleveland, recycled concrete sellers have to produce documentation showing their product is 4,000 or higher PSI. If they aren’t able to provide that documentation, their product is usually more difficult to sell.”

Take note

The properties and quality of recycled asphalt pavement can vary greatly, depending on the properties of the original materials used to create the mix. Quality can also be affected by the number of times a paved road was resurfaced, crack sealed and patched or seal coated.

Loretta Sorensen is a freelance writer in Yankton, S.D. She produces material on a variety of topics, serves as a ghostwriter, and has authored her own books. Additional information about Nelson Aggregate Co. is available at More details about the growth of recycled asphalt products in America may be found at

This article is tagged with , , , and posted in featured, Features
Avatar photo

About the Author:

Allison Kral is the former senior digital media manager for North Coast Media (NCM). She completed her undergraduate degree at Ohio University where she received a Bachelor of Science in magazine journalism from the E.W. Scripps School of Journalism. She works across a number of digital platforms, which include creating e-newsletters, writing articles and posting across social media sites. She also creates content for NCM's Portable Plants magazine, GPS World magazine and Geospatial Solutions. Her understanding of the ever-changing digital media world allows her to quickly grasp what a target audience desires and create content that is appealing and relevant for any client across any platform.

Comments are closed