Thermoreversible Aging Characteristics of Crumb Rubber–Modified Bitumen Based on Rheological and Fracture Mechanics Theories

In cold regions, bitumen exposed to low temperatures for an extended period undergoes thermoreversible aging, which can cause premature cracking of the bitumen pavement. The rheological properties and fracture characteristics of natural bitumen and crumb rubber–modified bitumen (CRMB) were examined using the extended bending beam rheometer (EBBR) test and single-edge notch bending (SENB) test, while under the influence of thermoreversible aging. The results show that thermoreversible aging can diminish the anticracking properties of bitumen, while CRMB exhibits superior low-temperature properties and resistance to thermoreversible aging. To accurately characterize the thermoreversible aging effect on the anticracking properties of CRMB using the EBBR and SENB tests, it is essential to maintain constant temperature test conditions for at least 48 h. Furthermore, under prolonged low-temperature conditions, the hardening crystallization rate of CRMB follows a normal distribution with decreasing temperature, with the fastest rate of hardening crystallization observed at −18℃. The hardening rate and thermal stress constitutive model provide a convenient calculation method for studying the change in stiffness modulus and thermal stress of CRMB under the thermoreversible aging condition. It also serves to lay a theoretical and technical foundation for the development, design, and application of road bitumen in cold regions.