Investigation of the Accuracy of Fracture Energy in Evaluating the Low-Temperature Cracking Performance of Asphalt Mixture

To study the reason why the evaluation result of fracture energy is sometimes inconsistent with in situ cracking, the accuracy of fracture energy in evaluating low-temperature cracking resistance of asphalt mixture was investigated. Firstly, the composition of fracture energy in the thermal stress restrained specimen test (TSRST), semicircular bending test (SCB), disk-shaped compact tension test (DCT), indirect tensile test (IDT), and three-point bending beam test (3PBB) was analyzed and the accuracy of fracture energy was discussed. Then, based on the defect of fracture energy, the evaluation index and test method in evaluating the low-temperature cracking resistance of asphalt mixture were proposed. Finally, some test results were used to verify the rationality of the proposed evaluation index. The results show that the fracture energy determined from TSRST, SCB, DCT, 3PBB, and IDT may be inaccurate to evaluate the low-temperature cracking resistance of asphalt mixture, as the fracture energy in these test methods is mainly the surface energy. If fracture energy was used to evaluate the low-temperature cracking resistance of asphalt mixture, it may choose a mixture with high modulus, poor relaxation performance, or fabricated by high surface energy materials. The dissipative energy caused by the stress relaxation should not be ignored when using energy as the evaluation index. The viscous dissipative energy obtained from DCT, SCB, or IDT at two different test temperatures was recommended to evaluate the low-temperature cracking resistance.