Asphalt pavements in colder climates encounter significantly shortened service lives because of excessive transverse cracking. This paper presents the results for 26 pavement sections in Minnesota that were studied to evaluate the effects of asphalt mix designs on pavement cracking performance. The field performance is presented with various cracking measures and compared with mix design aspects such as amount of asphalt binder, binder grade, and amount of recycling. The disk-shaped compact tension (DCT) fracture energies measured on the field cored samples are also compared with cracking performance. In this study, asphalt pavement sections from several locations were evaluated to encompass various types of asphalt mixtures and asphalt construction types that were commonly used in Minnesota. The amount of transverse cracking for each section was converted into a newly proposed cracking performance measure that accounted for the amount, rate, and timing of cracking. The comparisons between asphalt mixture attributes and cracking performance measures showed that the amounts of total asphalt binder and recycled asphalt binder may not be sufficient. Performance testing, in addition to currently used controls (mix volumetrics and constituent properties), is recommended to ensure good cracking performance. The DCT fracture energy results for companion sections show that mixtures with higher fracture energies exhibit lower amounts of transverse cracking.

In cold climate regions, thermal cracking of asphalt pavements is a major pavement distress. Cold climates cause a thermal contraction within the pavement. When combined with the brittle behaviour of asphalt at low temperatures, the thermally induced stresses are relieved by transverse cracks forming in the pavement. This cracking facilitates poor ride quality and premature failure of the pavement. There is currently no asphalt mixture performance test required by majority of Department of Transportations (DOTs) in the United States to address the issue of thermal cracking. Previous research has indicated that fracture energy of asphalt mixtures is a reliable predictor of transverse cracking performance. This mechanistic property of asphalt mixtures can be found using the disk-shaped compact tension (DCT) test. On basis of previous research, a low-temperature cracking performance specification that uses DCT fracture energy has been developed. During 2013 construction season, five construction projects were chosen to implement provisional specifications that use fracture energy as a required mix parameter. The projects encompassed different construction techniques, material compositions and climatic zones. The implementation procedure as well as the results from testing is presented in this paper. The results indicate a shift in the DCT fracture energy values between laboratory produced specimens that were provided as part of mix design acceptance and those manufactured using plant produced mix. Other findings include reaffirmation of common knowledge that use of higher binder contents and/or improved low temperature binder grades provide mixtures with improved fracture energies.

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