USE OF SCREENINGS TO PRODUCE HMA MIXTURES

Thin-lift hot mix asphalt (HMA) layers are utilized in almost every maintenance and rehabilitation application. These mix types require smaller maximum particle sizes than most conventional HMA surface layers. Although the primary functions of thin-lift HMA are to level the pavement surface, smooth the surface, and/or slow the deterioration of the existing pavement, these mixes may also provide some structural improvement, depending on the layer thickness placed. This study evaluated the use of manufactured aggregate screenings (fine aggregate stockpiles) as the sole aggregate portion of an HMA mixture. Mixes of this nature have the potential for use as thin-lift HMA layers. Two different sources of aggregate screenings, granite and limestone, were utilized to design mixtures at varying design air void contents and then tested for rut susceptibility. The use of a neat versus modified asphalt binder was also evaluated, as well as potential advantages of cellulose fiber additives. Mixtures using 100% manufactured screenings were most often shown to be acceptable with regards to rutting resistance. No work was performed in this study to look at thermal cracking or durability.