Using Recycled Asphalt Shingles with Warm Mix Asphalt Technologies (2018) / Chapter Skim
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1 Background New pavement technologies are continuously being developed and evaluated by highway agencies and the asphalt pavement industry to reduce the consumption of natural resources and costs of asphalt paving mixtures. Two technologies that have received substantial attention in the last few years are the use of recycled asphalt shingles (RAS)
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2 it is estimated that 210,344 tons of PC shingles are generated each year (Bauman 2005)
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3 the composite binder; (4) assessing the current range of asphalt mixture production temperatures; and (5)
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4 during the grinding process, minimizing such contaminants prior to processing is recommended (Grodinsky et al.
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5 Mix Design One of the most contentious parts of the RAS mixture design procedure is determining how much the RAS binder actually contributes to the overall binder content of the asphalt mixture. It is now generally accepted that less than 100% of the RAS binder is effective in the mix.
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6 source of RAS at 0%, 5%, and 10% by weight of aggregates. An AC-20 asphalt binder was used in the study, meeting the requirements for a PG 64-22.
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7 testing also showed a correlation between virgin binder content and dynamic modulus at the high-temperature portion of the master curve. The authors stated that the results provided justification for the current 70% minimum virgin binder criterion.
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8 binder had 20% cracking, and the virgin mix with SBS-modified binder had approximately 8% of the lane area cracked. The majority of the cracking in the test sections was low severity.
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9 There are three categories of WMA technologies: foaming, organic additives, and chemical additives. The NAPA surveys used a modified classification as follows: (1)
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10 The high-temperature grade of the mix containing RAS was the highest. Surprisingly, the recovered binder from the mix containing 50% RAP was the same grade as the mix with 15% RAP, and the high PG of the WMA virgin was higher than for the HMA virgin.
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11 Mixture Continuous Grade (°C) PG Control 62.2–31.2 58-28 40% RAP 72.4–27.9 70-22 5% RAS 65.6–32.2 64-28 35% RAP + 5% RAS 77.5–25.9 76-22 Control + 1% WMA 56.4–32.6 52-28 40% RAP + 1% WMA 64.2–30.9 64-28 5% RAS + 1% WMA 60.9–32.7 58-28 35% RAP + 5% RAS + 1% WMA 71.1–27.9 70-22 Source: Mogawer et al.
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12 Item 340. The control section mix design was based on the Texas DOT Special Specification Item 3000 for [Quality Control/Quality Assurance]
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13 The 2012 cycle of the NCAT test track included the Green Group experiment. One of the four test sections in the Green Group experiment included mixtures containing RAS in the surface and intermediate layers.
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