About the research
One of the primary asphalt pavement distresses encountered in Iowa is low temperature cracking. This distress manifests itself from the tensile stresses exceeding the elastic properties of the asphalt binder and/or inadequate asphalt binder content. Low temperature cracking increases maintenance costs of roadways, leads to water infiltration of the underlying pavement layers, and leads to reduced pavement life. Newer test methods have been developed for evaluating the low temperature cracking of asphalt mixtures and includes the disk-shaped compact tension (DCT) and semi-circular bend tests (SCB) while the asphalt binder specifications now include the multiple-stress creep recovery (MSCR) test. Both mix tests have been found to identify critical low temperature cracking of asphalt mixtures. The introduction of the multiple-stress creep recovery test for asphalt binders is improving the elastic properties of asphalt binders being used but alone is insufficient in evaluating mixture performance. The introduction of many different materials being blended with asphalt such as fluxes, rejuvenators, and compaction aids to attain performance grades or assist in construction is leading to use of materials with unknown low temperature mixture performance.
This research will evaluate the current performance of low temperature cracking of Iowa mixtures, and, if needed, propose adjustments to the performance criteria. Additionally, the research team will also work with other labs in the state with low temperature cracking testing equipment to understand the variability of the tests between labs. Based on the developed correlations, performance criteria for the DCT and SCB tests will be proposed.