Research conducted by Dr. Walaa Mogawer, professor of Civil & Environmental Engineering in UMass Dartmouth’s College of Engineering and his team at the Highway Sustainability Research Center (HSRC) has been selected as an American Association of State Highway and Transportation Officials (AASHTO) Sweet Sixteen High Value Research project for 2021. The research study was funded by, and conducted on behalf of, the Massachusetts Department of Transportation (MassDOT).
Every year, the AASHTO Research Advisory Committee (RAC) works with state agencies to identify and document recently completed “high-value” research projects. Each of the four RAC regions selects its top four projects to form the “AASHTO Research Sweet Sixteen Awards.” Selected projects are featured in AASHTO events, profiled in publications such as Research Makes a Difference, and highlighted at the Transportation Research Board Annual Meeting.
The goal of the performed study, titled “Characterization of Reclaimed Asphalt Pavement for HMA Surface Courses in MA,” was to understand the properties of the reclaimed asphalt pavement (RAP) sources available in Massachusetts and, based on these properties, to develop guidelines or recommendations for MassDOT to use RAP in new surface course paving mixtures. RAP is pavement material that is removed and reprocessed from existing roads. The main constituents of RAP are asphalt and aggregates; therefore, it provides an environmentally conscious alternative source for the main materials used in producing new pavements.
Using larger RAP contents conserves natural resources and can lead to significant economic savings. “A potential drawback to using more RAP is it contains a highly aged/oxidized asphalt binder, which is stiffer and more brittle as compared to a new asphalt binder,” says Mogawer who is director of the Highway Sustainability Research Center at UMass Dartmouth. “Using more of this stiff and brittle binder raises concerns that mixtures containing more RAP will be less durable, more prone to distress, and not last as long as pavements constructed solely of new materials. As a result, being able to accurately specify the correct amount of RAP to use in a paving mixture without sacrificing performance is of utmost importance.”
The results of the study demonstrated that one specific RAP percentage could not be used for all surface course mixtures in Massachusetts. A three-tiered approach was developed for MassDOT to properly specify RAP in a mixture in order to ensure that quality mixtures are produced, and the amount of RAP utilized is appropriate to maintain performance. To learn more about this project, watch the video and read the project brief.