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Combined Effect of Three-Dimensional Contact Load and Thermal Gradients on the Cracking Performance of Heavy-Duty Asphalt Pavements

Top-down cracking is well recognized as a major distress for heavy-duty asphalt pavements, yet the mechanism is not fully understood. Studies have indicated that nonuniform tire–pavement contact stress may play a significant role in the initiation of top-down cracking, and thermal stress caused by the temperature gradient may contribute to the initiation and development of top-down cracking. These relevant factors were evaluated with a sophisticated three-dimensional viscoelastic finite element model that was developed for studying the cracking performance of heavy-duty flexible pavements under combined three-dimensional tire–pavement contact stress and thermal stress induced by the temperature gradient. It was found that the stress distribution in asphalt concrete layers continuously changed as the pavement was loaded because of the rheological behavior of the asphalt concrete. Significant maximum principal tensile stresses are present at the tire edge at the asphalt concrete surface, which may result in an accumulation of dissipated creep strain energy over time (or with a cumulative number of loads) and may eventually lead to crack initiation. Additionally, near-surface pavement responses associated with top-down cracking under three-dimensional tire–pavement contact pressure are found to be more severe than those from uniform contact pressure. In a comparison with pavements without thermal effect, the negative temperature gradient increases the potential for top-down cracking, and the positive temperature gradient increases the potential for bottom-up cracking. The study provides insight into crack mechanisms, which may improve current heavy-duty asphalt pavement design procedures.