An investigation on perpetual asphalt pavements in Minnesota

Abstract

Asphalt Pavement Alliance (APA) created the Perpetual Pavement Award program in 2001. This program requires that the roadway has at least 35 years of service at the time of award and had experienced no structural failures. In addition, the program limits candidate roadways to those that have not received more than 100 mm of new asphalt nor have been resurfaced at a frequency exceeding 13 years. Minnesota Department of Transportation (MnDOT) currently owns the record for the most award winners and has received an award every year from 2002 through 2017. This study reviews all the award-winning roadways in Minnesota to determine common material, design factors and considerations which may have contributed to the roadways extended life, often exceeding 50 years, despite the harsh Minnesota climate. For these projects, all the available information and any pertinent supporting information were reviewed. Findings from this review showed that a combination of many different factors including large-scale subgrade correction, utilizing non-frost susceptible base and subbase materials, bituminous treatment of the granular layers, utilization of prime coat, and staged construction may have contributed to the outstanding performance of these award-winning roadways. In addition, a more in-depth analysis was performed on the four project locations within the Minnesota Metro District. To further investigate and characterize these sites, coring and hand auger borings were performed in cracked and un-cracked areas along with Dynamic Cone Penetrometer (DCP) test which the results indicated that the in-situ materials were strong in all the projects. The cores were then used to measure thicknesses, densities, asphalt contents, extracted gradations, and also to perform resilient modulus testing at low and intermediate temperatures. Resilient Modulus testing showed that the asphalt mixtures from different projects perform differently at intermediate temperatures, but this difference is much less pronounced at low temperatures. This could be one reason for the similar long-life behavior of these pavements, as they have been subjected to the low temperature condition in a substantial portion of their service life in the state of Minnesota.