LTC Pooled Fund - Phase II - Materials & Road Research

Investigation of Low Temperature Cracking in Asphalt Pavements - Phase II

Low temperature cracking is the most prevalent distress found in asphalt pavements built in cold weather climates. As the temperature drops the restrained pavement tries to shrink. The tensile stresses build up to a critical point at which a crack is formed. Thermal cracks can be initiated by a single low temperature event or by multiple warming and cooling cycles and then propagated by further low temperatures or traffic loadings.

The current Superpave specification attempts to address this issue by Winter Scene specifying a limiting low temperature for asphalt binders. However, the first phase of this project made it clear that testing asphalt mixtures is necessary to accurately predict low temperature cracking performance in the field. Furthermore, the testing must include more sophisticated techniques based on fracture mechanics rather than the current practice of stiffness and strength testing.

To this end, a comprehensive research effort is underway led by Dr. Mihai Marasteanu at the University of Minnesota. This project is a unique partnership between MnDOT and four universities: University of Minnesota, Iowa State University, University of Illinois at Urbana-Champagne, and University of Wisconsin at Madison. This project is using an integrated approach of laboratory mixture fracture testing, sophisticated modeling, and field evaluation to develop a low temperature cracking specification for asphalt mixtures. This pooled fund study will result in a tool that can be used by the 7 partner sponsors to select the optimal materials resistant to thermal cracking.