Evolution evaluation of high-speed railway asphalt concrete waterproofing layer during laboratory freeze–thaw cycles

Abstract

An in-depth understanding of internal freeze–thaw damage mechanisms in high-speed railway asphalt concrete waterproofing layer is of great importance to achieve its long-term waterproofing and mechanical performance during the prolonged service life. In this work, four types of composite polymerized railway asphalt mixtures with air voids of 2% were custom-designed and treated with a total of 20 modified freeze–thaw cycles. Meanwhile, the volume and mass measurement, X-ray CT, indirect tensile strength test, and Marshall stability test were used to characterize the internal freeze–thaw damage and evaluate the performance deterioration. The results indicated that the internal deterioration resulted from the generation, expansion, and aggregation of voids and micro-cracks. Meanwhile, a “lag effect” of the freeze–thaw damage, that is, a gradual inward erosion process, was verified by dividing the cylindrical specimens into the core layers, intermediate shell layers, and outer shell layers. The efficiency of the “lag effect” was influenced by the air void content in the outer shell layer, which meant the lower the air void content in the outer shell layer, the slower the freeze–thaw damage. In addition, all four types of asphalt mixtures exhibited promising waterproofing performance and freeze–thaw damage resistance. Binder A and AC-10 mixtures exhibited the superiority in terms of high-temperature performance and freeze–thaw damage resistance based on Marshall stability and flow value that were proved to have adequate efficiency on characterizing the freeze–thaw damage in railway asphalt mixtures.