Literature review of lower temperature asphalt systems

Abstract

A selection of the available literature on warm mix asphalt and half-warm mix asphalt were reviewed in order to ascertain whether some or all of the currently available technologies have a potential use on the UK Highways Agency's network. The review looked at the various categories of the technology, the differences required in site practices, the performance of the resulting asphalt and the environmental and economic advantages of their use. However, because there is considerably more literature than that included in this study, the findings can only be tentative. Construction Materials Literature review of lower temperature asphalt systems Nicholls and James

Warm-Mix Asphalt and Pavement Sustainability: A Review

“…According to Naidoo et al [21], the progress towards WMA deployment in South Africa was driven by the need and passion for environmentally sustainable road building solutions. The growing acceptance of WMA is based on confirmation of its economic, environmental and performance benefits relative to conventional HMA, and it is anticipated that WMA will soon become the standard practice within the industry [13] [17] [22].…”

“…Croteau and Tessier [17] have estimated that 20% to 35% energy savings in WMA production equates to 4.1 kg to 5.5 kg of CO 2 equivalent per ton of WMA. Accordingly, 0.4 million tons less CO 2 would be produced annually if the entire 63 million tons of asphalt produced in Germany were lower temperature asphalt, representing a potential reduction of about 25% [13]. Alderson [22] concluded from a review of studies in Australia that lower plant emissions were associated with WMA, noting that the actual reduction depended on the condition of the plant, type of fuel, weather conditions during production, and the type of technology used.…”

“…This translates to reduced fuel costs and results in savings that may range from 11% to 35%, which correspond to 1.5 -2.0 liters of fuel per ton of WMA mix [12] [17]. Anderson and May [27] as cited by Nicholls and James [13] found that reduction in production temperature by 10˚C results in energy savings of 3% to 4%, which corresponds to about 0.25 kg fuel per ton of asphalt produced. NAPA [8] indicates that WMA reduces fuel consumption during production by an average of 20%, which decreases total life-cycle greenhouse gas emissions by 5%; the energy savings is equivalent to cutting one million tons of asphalt production annually.…”

“…It is argued by some that fuel savings from WMA production may not be substantial to immediately offset the cost of the initial investment [27] as cited by Nicholls and James [13]. However, other benefits of WMA, such as increased production or late season paving, provide additional economic incentives [13].…”

“…To address these concerns, the asphalt industry has developed warm-mix asphalt technologies that enable the production of asphalt mixes at temperatures that are 20˚C -40˚C lower than conventional HMA production temperatures. The lower production temperatures are as a result of reduction in binder viscosity achieved through rheological modification while providing for complete coating of aggregates and workability of the mix at lower temperatures with the expectation that the mix possesses strength, durability, and performance characteristics similar to or better than HMA [12] [13].…”