NVF 33 Annual Meeting, June 2007 Trondheim, Norway 1 Ólöf Kristjánsdóttir W ARM MIX ASPHALT TECHNOLOGY ADOPTION Ólöf Kristjánsdóttir, Transportation Engineer VGK-Hönnun Consulting Engineers Reykjavik, Iceland [email protected] INTRODUCTION Warm mix asphalt (WMA) is the broad term typically used for technologies that seek to lower emissions and reduce energy consumption by lowering the temperature at which asphalt mixtures are produced and placed. This paper examines the costs, benefits and risks associated with WMA technologies in an attempt to determine their most promising implementation path. By looking at basic economic calculations, a survey of the Icelandic pavement industry and results from two projects in Maryland, U.S.A., the conclusion is drawn that it is unlikely that lower emissions and reduced energy consumption will be the catalysts for widespread WMA use because currently these benefits only overcome WMA costs in isolated scenarios. Reduced viscosity, however, makes the best business case for widespread WMA technology adoption because this benefit offers cost and risk reduction. Although this paper examines published cost estimates and evidence of certain WMA benefits, these numbers should not be construed as an endorsement of any particular WMA technology over another. Further, the rigor of this paper is not in the detailed material property analyses but rather in a fair assessment of the business case for WMA adoption. This article is a shortened version of a paper that was written in 2006 by Ólöf Kristjánsdóttir, Stephen T. Muench, Assistant professor at the University of Washington, Larry Michael, LLM Asphalt Technology Consulting and Gloria Burke, Maryland State Highway Administration, for publication at the TRB 86 th Annual Meeting, and was based on the work done by Ólöf Kristjánsdóttir for her masters thesis at the University of Washington in 2006. PRINCIPAL TYPES OF WARM MIX ASPHALT (WMA) With HMA, heat is used to dry aggregate and reduce asphalt viscosity so that the asphalt will adequately coat the aggregate during mixing. With WMA, the heat is reduced and the asphalt viscosity reduction is assisted by (1) introducing water, chemicals or wax as an additional lubricant in the mixing process, (2) foaming the asphalt, or (3) combining the asphalt with water or other chemicals as in an emulsion. Currently, there are several substantially different methods for producing what is broadly termed WMA (Table 1).
WARM MIX ASPHALT TECHNOLOGY ADOPTION
Jun 24, 2023
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