Mechanical Properties of Warm Mix Asphalt Prepared Using Foamed Asphalt Binders : Executive Summary Report

Executive summary report.PDFBooklet/PamphletFHWA/OH-2011/6134476Hot mix paving mixturesWarm mix paving mixturesRuttingTensile strengthFoamed asphaltOhioOhio. Dept. of Transportation. Innovation, Research, and Implementation SectionAbbas, Ala R.Ali, AymanUniversity of Akron. Dept. of Civil EngineeringOhio. Dept. of TransportationNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsUS Transportation CollectionHot mix asphalt (HMA) is a mixture containing aggregates and asphalt binders prepared at specifiedproportions. The aggregates and asphalt binder proportions are determined through a mix designprocedure such as the Marshall Mix Design or the Superpave Mix Design methods. Overall, the goal ofdetermining such proportions is to establish an HMA mixture that will meet specific performance criteria.In addition, it is imperative to ensure that the asphalt binder will fully coat the aggregates and that theresulting mixture is workable and compactable.In order to ensure sufficient aggregate drying and coating, both the asphalt binder and the aggregates areheated to elevated temperatures ranging between 300oF and 325oF. The use of such high temperatureswould result in lowering the viscosity of the asphalt binder which is the main factor affecting the coatingand workability of asphalt mixtures.In recent years, a new group of technologies have been introduced to the United States that allowproducing asphalt mixtures at temperatures 30 to 100oF lower than what is used in HMA. This group oftechnologies is commonly referred to as Warm Mix Asphalt (WMA). They are promoted asenvironmentally friendly green alternatives to HMA mixtures as they produce lower greenhouse gasemissions. This new group of technologies aims at reducing the viscosity of the asphalt binder throughthe addition of organic or chemical additives or by introducing cool water into the heated molten asphaltunder controlled temperature and pressure conditions, resulting in so-called foamed asphalt binder. As aconsequence, lower temperatures are needed during production for the asphalt binder to be absorbed bythe aggregates