Development and Field Evaluation of Energy-Based Criteria for Top-down Cracking Performance of Hot Mix Asphalt

摘要

It is now well-recognized that top-down cracking is a major form of distress in hot mix asphalt pavements A detailed analysis and evaluation of 22 field test sections throughout the state of Florida resulted in the development and verification of energy-based criteria for top-down cracking of hot mix asphalt. The work clearly indicated that there is no single mixture property or characteristic that can reliably predict top-down cracking performance of hot mix asphalt. A parameter termed the Energy Ratio, which was derived using the HMA Fracture Mechanics Model developed at the University of Florida, was determined to accurately distinguish between pavements that exhibited top-down cracking and those that did not, except for mixtures with excessively low or unusually high dissipated creep strain energy thresholds. The Energy Ratio, which is defined as the dissipated creep strain energy threshold of the mixture divided by the minimum dissipated creep strain energy required, is determined on the basis of tensile properties that can be obtained from a modulus, creep, and strength test performed with the Superpave IDT at a temperature of 10°C. The Energy Ratio accounts for the effects of pavement structural characteristics on top-down cracking performance. Therefore, it can be used to suitably integrate asphalt mixture properties in the pavement design process. In addition, a rational approach was developed to adjust the minimum Energy Ratio criterion for different traffic level pavements. In conclusion, two energy-based criteria were recommended to control top-down cracking of hot mix asphalt: 1) a minimum dissipated creep strain energy threshold; and 2) a minimum Energy Ratio for mixtures with a dissipated creep strain energy threshold greater than the minimum.