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Impact of Alternative Asphalt Binder Extenders on Asphalt Mixture Design, Production and Performance
AuthorHand, Adam J.T.
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Historically there has been fluctuations in asphalt binder cost and at times supply shortages. After the 1973 Oil Crisis and 2008 asphalt binder price peak, efforts to responsibly increase the amount of RAP and RAS in asphalt mixtures increased. Several alternative binders or extenders were introduced into the market following each event. Since the 2008 peak in asphalt prices and relatively high cost of asphalt binder from 2011-2015, the desire to increase RAP/RAS continued to drive alternative binder development and refinement. This has also been driven by the industries desire to continually be more sustainable. The question of whether true alternatives to petroleum based binder exists, or will exist in the near future, and can be viable has repeatedly been asked since the 2008 price peak. The asphalt industry recognized potential for price and supply instability and invested in keeping up with alternative asphalt binder and extender developments, in preparation for potential future extremes that could impact operations. There are several considerations as to how alternative asphalt binders and extenders could impact asphalt binder and mix performance, as well as production and construction operations. An extensive literature review, web-based industry stakeholder survey, and a set of 27 industry expert stakeholder interviews were conducted to answer the question, “What does an asphalt contractor need to know about potential impacts of using alternative asphalt binders and extenders?” Currently available alternative binders and the impact of them on mix design, production and construction were identified and summarized. Available alternative binders are bio-based, recycled oils or tall oil from paper manufacturing. There are alternative binders available for use in relatively low doses (≤10% of virgin binder mass) with conventional asphalt that support high binder replacement (up to 50%) mix designs when coupled with good quality virgin binders and RAP/RAS management. There will likely be changes in asphalt binder, recycling agent and mix design standards in the near future that will require producer investment in equipment and employee training and development to leverage alternative binders. Like asphalt binders, alternative binders are commodities susceptible to market conditions.