Low-temperature cracking resistance of asphalt concretes for railway substructure exposed to repeated freeze-thaw cycles

The waterproofing substructure under high-speed railway track is of importance to avoid the infiltration of surface water and maintain the bearing capacity of railway subgrade. In this study, the low-temperature cracking resistance of composite polymerized asphalt concretes for high-speed railway waterproofing layer (shortened to railway asphalt concretes) was investigated when exposed to freeze-thaw cycles. Although the measured maximum load, fracture energy and fracture toughness indicated a certain degree of low-temperature performance deterioration after repetitive freeze-thaw cycles, railway asphalt concretes showed excellent moisture susceptibility in this regard. In addition, the railway asphalt concretes prepared with binder B and gradation AC10 were generally superior to their counterparts in this respect. On the other hand, the image processing of specimens' fracture surfaces indicated that the cracking of railway asphalt concretes at low temperatures could be mainly attributed to the binder cohesion failure. Besides, the contribution rate of aggregate-binder adhesion failure to the overall cracking gradually exceeded that of aggregate fracture with the increased freeze-thaw cycles. Finally, a statistically significant correlation between the fracture energy and interfacial adhesion failure was found. This implied that the deterioration of low-temperature cracking resistance could be primarily contributed to the reduced aggregate-binder adhesion strength during freeze-thaw cycles.