Assessing potential for warm-mix asphalt technology adoption

Warm-mix asphalt (WMA) describes a range of technologies that seek to lower emissions and reduce energy consumption by lowering the temperature at which asphalt mixtures are produced and placed. Despite these benefits, reduced mixture viscosity may be the most likely reason for widespread adoption of WMA technologies. Hot-mix asphalt (HMA) producers are unlikely to adopt WMA technologies solely to lower emissions, because current environmental regulations and the relatively clean nature of HMA plants make lower emissions unnecessary and unprofitable except in select air pollution areas. Producers are also unlikely to adopt WMA technologies solely to reduce energy consumption, because energy savings are less than the associated costs except in the most expensive energy markets. Reduced viscosity makes the best business case for widespread WMA technology adoption, because this benefit offers cost and risk reduction: it can (a) alleviate compaction problems associated with cool weather, (b) reduce compaction equipment needs at the job site, and (c) lower the risk of poor compaction when working with stiff mixtures. This conclusion is supported by basic economic calculations, a survey of the Icelandic pavement industry showing strong support for WMA technology use to improve cool weather paving, and two projects in Maryland showing the potential for WMA technology use to lower the risk of poor compaction of high reclaimed asphalt-pavement mixtures.