Using Recycled Asphalt Shingles with Warm Mix Asphalt Technologies (2018) / Chapter Skim
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163 Activation Energy for Recycled Asphalt Shingle Binders and Dispersion of RAS in Asphalt Mixtures Abstract The thermal energy input required to achieve recycled asphalt shingle (RAS) asphalt binder phase change from solid to liquid is assumed to provide an indicator of how well RAS particles break down during mixing, allowing the RAS binder to become an active part of the mixture's composite binder.
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164 Sample Preparation and Testing Sample preparation included sieving a sample of processed RAS into 13 particle size ranges (45, 150, 250, 300, 350, 500, 600, 710, and 850 µm; and 1, 2.23, 4.04, and 7.26 mm)
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165 (Figure B-3)
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166 shingles are composed of silicon, calcium, aluminum, and oxygen. Figure B-6 illustrates that the asphalt matrix of the RAS is composed essentially of carbon, with small amounts of oxygen and sulfur.
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Figure B-4. Scanning electron micrograph using backscattered electrons of a PC–RAS stock illustrating the contrast seen between fiberglass fibers and RAS matrix.
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168 gold sputter coated to provide electrical conductivity during SEM analysis. The coated samples were mounted on aluminum stubs, and images were taken at various magnifications with a JEOL 7000F SEM.
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169 (a) 45µm before (top row)
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170 as an indicator of RAS presence in asphalt mixtures. In addition to EDS chemical analysis, the fibers have a unique shape compared to the minerals in the aggregates containing silicon.
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171 a thin gold layer to make the surfaces conductive. Unfortunately, SEM imaging did not reveal the presence of the fibers on the surfaces (Figure B-9)
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172 were used, but it was found that these materials were too dangerous for the technicians. An over-the-counter commercial asphalt and tar remover (Black Jack)
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173 considered a feasible technique to quantify dispersion, much less validate the hypothesis that the fiber dispersion could be an indicator of RAS binder activation. Perhaps analyzing hundreds of samples that were randomly obtained from a larger quantity of mix produced with RAS could provide a better statistical measure of dispersion, but the cost of doing so would be prohibitive.
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