Low temperature characteristics of asphalt mixture based on the semi-circular bend and thermal stress restrained specimen test in alpine cold regions

Abstract

Low-temperature crack resistance performance for preventing and controlling asphalt pavement cracking plays an important role in alpine regions. This study is to evaluate the low temperature characteristics of asphalt mixture in alpine cold regions. Three kinds of asphalt binders (SK90, SBS modified asphalt, SRA modified asphalt-an independent R & D type for the alpine cold regions) and three types of gradations (AC-13, AC-16, SMA-13) were selected. The fracture characteristics of asphalt mixtures based on the energy perspective were evaluated based on the semi-circular bend (SCB) test. The influences of asphalt binder type, gradation type, temperature and notch depth on the stress–strain curve were investigated. In addition, the thermal contraction coefficient of different kinds of asphalt mixtures were also analyzed. The temperature stress curves of asphalt mixtures were constructed based on the thermal stress restrained specimen test (TSRST). The results showed that the distribution characteristics of the coarse aggregate had a greater impact on the cracking path of the specimen. The asphalt mixture specimen exhibited brittle fracture at −15 °C and −35 °C, while it exhibited ductile failure at 15 °C based on the stress–strain curves. The unit reference fracture energy can be used as an effective index to evaluate the crack resistance. SRA asphalt mixture specimens had the largest fracture toughness and unit reference fracture energy. The higher the notch depth, the smaller the fracture energy; the fracture energy and the incision had a good linear correlation. The thermal contraction coefficients of SRA, SBS and SK90 asphalt mixtures were 10.46 × 10-6 ∼ 18.65 × 10-6/°C, 10.66 × 10-6 ∼ 22.85 × 10-6/°C, 13.45 × 10-6 ∼ 28.80 × 10-6/°C, respectively; they were closely related to the asphalt type and temperature, it changed exponentially under different temperatures. The freeze-break temperature was within a range and the difference was within 5 °C. SMA-13 had the strongest low-temperature crack resistance, followed by AC-16, and AC-13.