Cracking Performance Evaluation of Minnesota Asphalt Pavements

Abstract

Thermal cracking is the most prevalent distress for asphalt roadways in Minnesota. The cracks form pathways for water to permeate into the pavement structure degrading its integrity and shortening the life span. This thesis investigates asphalt mixture design parameters and laboratory tests measures of 25 pavement sections on 18 highways in Minnesota to draw conclusions on how these parameters relate to transverse cracking performance. The results showed that the coarse gradation of asphalt mixes currently being used by MnDOT typically have higher permeability rates than the typical range for dense graded asphalt mixtures, which makes these pavement sections more susceptible to moisture-induced damage. Next, this study analyzed the transverse and longitudinal field cracking performance of 295 pavement sections on 28 highways with respect to their asphalt binder type and polymer modification. The effect of asphalt binder type and modification was compared to field cracking performance in relation to construction type, asphalt binder supplier, and dynamic shear rheometer parameters: phase angle and dynamic shear modulus. The polymer-modified PG58-34 binder performed better than the non-polymer modified version. The last part of this thesis evaluated the sensitivity of flexible pavement thermal cracking performance to variations in disk-shaped compact tension (DCT) fracture energy. This study included nearly 200 simulations representing combinations of 3 climates, 3 asphalt thicknesses, 3 asphalt mixtures and 6 fracture energy levels. The motivation of this work was to investigate the sensitivity to the 400 J/m2 threshold that is being used in the implementation of the DCT performance test specification. It is concluded from this study that variation of 25 J/m2 is enough to show a difference in cracking performance.