, Former Assistant Professor, UMD-Civil Engineering
The asphalt mixture design and acceptance procedures for the Minnesota Department of Transportation (MnDOT) are currently governed primarily by the mixture composition requirements put forth through use of various volumetric measures (such as air content, asphalt film thickness, aggregate gradation, etc.). The asphalt binder has been required to meet performance criteria through the Superpave asphalt binder specifications. This study looked at use of laboratory performance test for asphalt mixtures. The study was conducted in three phases. The first phase focused on merging the asphalt mix design records with the pavement performance data to determine effects of mix design parameters on asphalt pavement cracking performance. The second and third phases used a series of field sections across Minnesota to conduct field performance evaluations as well as laboratory tests on field cored samples. The testing for the second and third phases of the study focused on using disk-shaped compact tension (DCT) fracture energy test as a laboratory performance test. The findings from the first phase of study indicated that the asphalt binder type as defined by the Superpave performance grade (PG) plays an important role in affecting the field cracking performance. The majority of mixture design parameters did not indicate a consistent effect on field cracking performance, which reinforces the need for use of laboratory performance test as a mixture design tool as well as acceptance parameter. The DCT testing results showed trends consistent with previous and other ongoing research studies, whereby the asphalt mixtures with higher fracture energies corresponded with pavements with a lower amount of transverse cracking.