Top-Down Fatigue Cracking in High-Temperature Environments

Abstract

Top-down fatigue cracking (TDFC) is now recognized as a common type of distress occurring in all types of environments on heavy-duty hotmix asphalt (HMA) pavements, but TDFC modeling is still limited in current state-of-the-practice tools. Despite significant recent advances in TDFC modeling, for regions with high-temperature seasons an extreme high-temperature profile with depth is a potentially important factor that deserves further consideration. This paper explores the potential of temperature gradients caused by high pavement surface temperatures to induce TDFC. Although, for the Hawaii environment, the Mechanistic–Empirical Pavement Design Guide (MEPDG) always predicts that the HMA modulus decreases with depth after some aging of the pavement, the study results indicate that for some plausible high-temperature profiles the HMA modulus increases with depth even when frequencies are computed with the MEPDG procedure. This increase results in the greatest tensile strains, maximum shear strains, and estimated damage occurring near the top of the HMA layer at the edge of the load. The apparent inconsistency is attributed to the coarse modeling of temperatures within a season in the MEPDG; this coarse modeling may result in such high-temperature profiles not being modeled. A modification of the MEPDG procedure to refine the modeling of environmental effects at high temperatures (e.g., including the 95th and 98th pavement temperature percentiles) is recommended. This modification would allow better modeling of TDFC with the traditional approach.