Warm Mix Asphalt: European Practice

FHWA-PL-08-007

A number of new technologies have been developed to lower the production and placement temperatures of hot mix asphalt (HMA). Generically, these technologies to reduce production temperatures are referred to as warm mix asphalt (WMA). These technologies originated in Europe in response to a variety of concerns.Beginning in 2002, interest in these technologies has grown in the United States (U.S.). The American Association of State Highway and Transportation Officials (AASHTO) and the Federal Highway Administration (FHWA) organized a scanning tour to Europe, allowing U.S. experts to meet first hand with the agencies who first used these technologies, the suppliers and contractors who developed them, and the contractors who build WMA pavements. The tour also allowed the team to view the performance of some of the oldest WMA projects in Europe.

A team of thirteen materials experts from the U.S. visited four European countries, Norway, Germany, Belgium, and France, in May 2007 to assess and evaluate various technologies for reducing the temperatures at which hot mix asphalt (HMA) is mixed and compacted. The scan team represented a wide variety of HMA interests in the U.S. including state agency AASHTO representatives, FHWA representatives, asphalt supplier and HMA contractor industry representatives, and a consultant. The team learned about a wide range of technologies, discussed with various agencies how and why they were implementing these technologies, visited construction sites, and viewed in-service pavements. In addition, the team tried to understand how conventional HMA practice differs between the U.S. and the various European countries and how these differences might affect potential implementation in the U.S.

The information obtained during the trip identified several implementation items to further the use of WMA in the U.S. This document provides preliminary descriptions of the findings and recommendations of the team. A separate report is currently being prepared that will provide a full description of the findings and recommendations from this trip.

The report will be available in March 2008

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• Trip Summary