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RAS Best Practices

RAS Best Practices. PAPA 54th Annual Paving Conference Hershey, PA January, 30th 2014. RAS Best Practices. What is RAS?. RAS Best Practices. Recycled Asphalt Shingles. Types. 2 types of roofing shingle scraps:

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RAS Best Practices

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  1. RAS Best Practices PAPA 54th Annual Paving Conference Hershey, PA January, 30th 2014

  2. RAS Best Practices What is RAS?

  3. RAS Best Practices Recycled Asphalt Shingles

  4. Types • 2 types of roofing shingle scraps: • Tear-offs generated during the demolition or replacement of existing roofs • Manufactured waste generated when new asphalt shingles are trimmed during production to the required physical dimensions or from "out-of-spec" shingles

  5. Composition Shingles typically contain: • Asphalt binder • Tear-offs contain 20 – 40% binder • Manufacturer waste 18 – 22% binder • 40 to 60% hard rock granules and fillers • 1 to 12 % fiber, felt, and miscellaneous materials

  6. Industry Guidance NAPA IS 136: Guidelines for the Use of Reclaimed Asphalt Shingles in Asphalt Pavements

  7. Where?

  8. Experience • Incorporating RAS into HMA began more than 30 years ago • Pennsy Supply began using shingles in PA in 2002 • PennDOT currently only allows Manufactured RAS, but may be considering allowing use of Tear-Offs

  9. Environmental Concerns • Similar concerns as for aggregate crushing, RAP processing/crushing & HMA production • Asbestos screening (if using tear-offs) • Must comply with local agency requirements, which vary from state to state

  10. Environmental Benefits • HMA mixtures produced with shingles are 100% recyclable • Saves natural resources • Saves landfill space

  11. Processing Shingles • Various types of industrial grinders can be used to grind the Shingles into a usable product • Most use shredding approach • Water is used during processing for dust suppression and to aid in shredding, but must be controlled

  12. Processing Shingles • Separate out the non-shingle debris before incorporating into HMA • Keep all non-shingle debris separated

  13. Processing Shingles • Ensure proper sizing of the ground Shingle particles • Finer is better • Oversized Shingle particles impact: • Contribution to Pbe • Mat texture

  14. Processing Shingles • Test RAS for gradation & AC Content frequently as they are being shredded • Keep RAS of different AC contents in separate stockpiles

  15. Processing Shingles Pre-Processing Post-Processing

  16. Processing Shingles • In some cases RAS is blended with a carrier aggregate: • Used to keep Shingles from conglomerating & allows for more efficient flow through cold feed bin • RAP, 3/8” Stone, washed screenings, Natural Sand can be used

  17. Storage • Store RAS in covered environment to control moisture • Shingles left exposed to rain can have very high moisture contents (12%+) • RAS holds more moisture than RAP

  18. Plant • Not always a best practice to keep the shingles bin full • Best practice to empty the shingles bin when production complete or production is stopped for extended period Photo courtesy of Astec Industries

  19. Plant • Ensure the RAS feed system is calibrated and maintained Photo courtesy of Astec Industries

  20. Plant • Load cells or weigh belts measure the amount of RAS as it is metered into plant Photo courtesy of Gencor Industries

  21. Plant • Watch for build-up at the RAP collar, especially for plants with smaller throats

  22. Plant • Consider covering conveyors and transfer points

  23. Plant • Test moisture content of RAS often while incorporating into mix – even more frequently if RAS stockpiles are not covered

  24. Plant • RAS has been used successfully in batch and drum facilities • May need to increase dry & wet mix time in batch plants

  25. Temperatures Higher plant production temperatures may be needed to ensure all moisture is removed from RAS & to maximize blending of RAS binder with virgin binder

  26. Temperatures Higher plant production temperatures may be needed to ensure all moisture is removed from RAS & to maximize blending of RAS binder with virgin binder

  27. Field • RAS mixtures can behave differently than virgin mixtures or RAP mixtures, which doesn’t necessarily make them bad: • RAS mixtures tend to be more sensitive to fluctuations in production temperatures • RAS mixtures are typically stiffer so may require additional effort to compact • RAS mixtures may make hand-work more difficult , so think through paving sequence before you begin paving

  28. Summary • Shingles require processing • Need consistent stockpiles of RAS • Should cover stockpiles of RAS • Test gradation & moisture content of RAS often • RAS feed must be calibrated & controlled • Higher production temperatures may be needed • Be prepared to manage deltas in mix characteristics when placing RAS mixtures

  29. Thank you

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