Dem Con News

In a presentation at the 2010 TERRA Pavement Research Conference, Curt Turgeon, a pavement engineer at Mn/DOT’s Office of Materials, discussed the department’s use of asphalt obtained from tear-off roofing shingles scrap (TOSS) in pavement.

Nothing that about 230,000 tons of discarded shingles go into Minnesota’s landfills every year, Turgeon said there was initial enthusiasm about this source of asphalt when it was first discussed several years ago.  “But then reality set in!  People pointed out that shingle asphalt is not paving asphalt.  They worried that spending 10 to 30 years on a roof probably doesn’t improve the asphalts’ qualities.  Furthermore, shingles come off roofs along with a lot of junk—and they might contain asbestos.”

Accordingly, Turgeon said, it was decided that there would need to be both quality control and limitations on how much asphalt from TOSS could be included in pavements.  To address the asbestos issue, the Minnesota Pollution Control Agency funded a Mn/DOT research project.  Testing The office of Materials test 17 different asphalt samples with varying combinations of asphalt from four sources:

• Tear-off roofing shingle scrap (TOSS)
• Manufactured waste shingle scrap (MWSS)
• Reclaimed asphalt pavement (RAP; all from a shingle source except in one formulation)
• Virgin Asphalt

A chemistry test showed that, when subjected to bending stress, four of the samples (see table) with formulations likely to be used in pavements had essentially identical properties.

Another test showed that, in general, the more old asphalt from tear-off shingles is included in a mix, the stiffer the mix is at low temperature—and therefore the more likely it is to exhibit thermal cracking.

Asbestos in pavement?

Turgeon referred to the possibility that TOSS might contain asbestos as a “lighting rod issue”. However, in tests conducted by a third-party laboratory on more than 1,000 samples taken from DemCon, a shingle recycler in Shakopee, Minnesota, no asbestos has yet been found, he reported.  Turgeon directed anyone with questions about the asbestos issue to Wayne Gjerde at wayne.gierde@pca.state.mn.us.

Purity standards

Turgeon also discussed strategies for avoiding contaminants in TOSS.  Working with DemCon, Mn/DOT has developed a four-part strategy:

• Charge roofers less if they pre-sort and bring in cleaner loads.
• Workers pull out the largest non-shingle material such as boards and pallets.
• Workers hand-sort materials moving past them on a conveyor.
• Run the resulting material through a shredder that also pulls out nails with magnets.

Mn/DOT’s standard for the resulting material is that 100 percent must pass through a ½-inch sieve, 90 percent must pass a #4 screen and there must be less than .05 percent “deleterious material”. Turgeon added that the maximum amount of deleterious material is half a percent of five percent—that’s pretty low.  However, a slightly larger pieces of TOSS occasionally gets through—so you have a little ‘tab’ popping up on the surface of the pavement, and that doesn’t seem to be much of a problem.” Standards for MWSS and TOSS are part of Mn/DOT’s bituminous standard and can be found at www.dot.state.mn.us/materials/bituminousdocs/Special_Provisions/2009/Shinlges/Table%202360.3-B2_Agg_Reg_2010.pdf.  LTAP –Richard Kronick, LTAP freelancer

Source: Minnesota Technology Exchange: ‘Pavement Conference’

Recycling of tear-off asphalt shingles is ready for full-scale, commercial operations.  That’s the message from two companies that sponsored a special event held in Shakopee, MN on October 21.  The main barrier is the need for a permissive materials specification from the Minnesota Department of Transportation (MnDOT).

Dem-Con Recovery & Recycling, a subsidiary of Dem-Con Companies, is a local recycling company that has recently invested in the equipment and systems needed to turn tear-off shingles into a culpable recycled product.

Once residential asphalt shingles have been sorted and cleaned to remove contaminants and then ground, the product can be introduced into the mix at hot mix asphalt (HMA) plants.

One recent study indicated that on a statewide basis, tear-off shingles recovery could reach at least 156,000 tons per year by 2012.  Given the oil content within tear-off shingles (at least 20 percent), about 32,000 tons per year of binder (virgin liquid asphalt oil) would be conserved by recycling shingles into HMA pavement.

Rotochopper Inc. is the equipment manufacturer that sold its “RG1” grinder to Dem-Con.  “We have seen numerous successful tear-off shingles recycling businesses around the United States and Canada” says Vince Hundt, vice president of Rotochopper.  “Our RG1 grinder can produce a high-quality, finely ground RAS product in one pass.  Recyclers like Dem-Con will be able to sell a valuable recycled product to HMA producers”.

Plehal Blacktopping installed the asphalt pavement at Dem-Con’s Shakopee plant.

“Our paving crew didn’t notice any difference,” says Jack Van Remortel, president of Plehal Black-topping. “The bituminous mixture was installed using normal equipment and procedures.”

MnDOT has been a leader in the country among other state departments of transportation when it adopted an earlier specification in 1996 for the use of manufacturers’ shingle scrap for use in HMA.

This “new” shingle scrap comes from the three shingle manufacturers located in Minnesota.  Since then, MnDOT has participated in five demonstrations of road construction projects that have successfully incorporated tear-off or “used” shingles into HMA pavements.

MnDOT is currently considering how best to write requirements for an updated new materials specification that would allow tear-off shingles in HMA.

Source: Asphalt Contractor December 2008, Paving Innovations

Dem-Con Recovery & Recycling, a subsidiary of Dem-Con Companies, Shakopee, Minn., is ready to recycle tear-off asphalt shingles and is awaiting for the proper materials specification to be developed by the Minnesota Department of Transportation (McDOT) in order to meet market demand.

CMRA member Dem-Con is a mixed C&D recycling company that has recently invested in the equipment and systems needed to turn tear-off shingles into a valuable recycled product.  Once residential asphalt shingles has been sorted and cleaned to remove contaminants and then ground, the product can be introduced into the mix at hot mix asphalt (HMA) plants.  HMA plants manufacture asphalt mix that paving companies use for making flexible bituminous pavement for roads, parking lots, driveways.

Commercial Asphalt Co., a nearby HMA producer, has successfully tested the use of asphalt shingles (RAS) material produced by Dem-Con. Commercial Asphalt, a subsidiary of Tiller Corp., manufactures high-quality asphalt.  Commercial has been making and using recycled asphalt pavement (RAP) from old bituminous roads for more than 20 years.  Commercial has extensive experience with the quality control procedures needed to produce high quality products.  They believe the time has come for tear-off shingles to be a part of a viable HMA product.

“Recycling of tear-off shingles will be a significant new step forward in abating the need for land filling shingles,” said Jason Haus, vice president, Dem-Con. “Our landfill along receives about 50,000 tons per year of roofing waste.”

Dem-Con is serious about is commitment to produce the highest quality tear-off RAS product. “Based on other demonstrations in Minnesota and in other states, we not only invested in a new shingle grinder, but also a sorting and cleaning system to assure we can meet any material specification our customer’s needs,” said Haus.  “The quality and cleanliness of the RAS will differentiate companies that are looking to enter this market.  We have received samples of very high quality and low quality RAS and the main difference is the effort put forth to ensure the cleanliness of the product.  The cleaning and sorting process to eliminate foreign debris is critical in producing a high quality RAS.

“The next neede step for large scale recovery of tear-off shingles if a permissive MnDOT specification similar to the specification granted for manufactured scrap shingles,” said Haus.

“Once the permissive specification is determined and assuming virgin asphalt prices remain high, the land disposal of shingle material will become rare.  Our industry is prepared to provide his material to HMA producers on a large scale.  Without the MnDOT space, we will have to continue land filling valuable tear-off shingles.  We have a great opportunity to reduce materials being land filled while providing a substitute for virgin asphalt at a lower price.  Recycling and positive economics have always been a large debate within the solid waste field and with recycled asphalt shingles, there is very little debate, it just makes sense.”

“We have the capacity to do this,” said Robert Keuhborn, manager of product design/quality control, Commercial Asphalt. “Recycling tear-off shingles is now a well proven, feasible technology.  When we bring this new technology up to full scale, it will help us conserve asphalt cement and save money.  Part of this savings can be passed along to the driving public.  The time has come for tear-off asphalt shingles to be accepted as another standard recycled material into hot mix asphalt.  Tear-off shingles should be part of permissive materials specification similar to the way RAP and manufacturers’ asphalt shingle scrap are considered by MnDOT today.  In order to consume any meaningful quantity of tear-off shingles, the HMA industry needs a permissive specification because we want to produce MnDOT certified mixes on a standard, full scale basis.”

One recent study indicated that on a statewide basis, tear-off shingles recovery could reach at least 156,000 tons per year by 2012.  Given the oil content within tear-off shingles (at least 20%). About 32.000 tons per year of binder (i.e., virgin liquid asphalt oil) would be conserved by recycling shingles into HMA pavement.  Using a conservative price estimate of $400/ton of liquid virgin binder, this savings has an equivalent of about $12.5 million.

Source: C&D World: Industry News – January/February 2009