Low-temperature performance of SBS modified asphalt mixture in high altitude and cold regions

Due to the severe natural environment found in high-altitude and cold regions, where the altitude is around 4000 m, and the average annual temperature is below 0°C, the design method and quality indicators of asphalt mixture performance is different in comparison to inland cities. To optimize design parameters and low-temperature performance of SBS modified asphalt mixture in high-altitude and cold regions, the beam bending, splitting, aging, and freez-thaw cycle tests were conducted based on the test protocol, field experience and quantitative analysis. Standard mixing procedures and evaluation indexes for low temperature anti-cracking performance were used to reveal the low temperature decaying characteristics of SBS modified asphalt mixtures. The results show that the optimum binder-aggregate ratio of 5.3% and the optimum SBS modifier dosage of 4%∼5% are recommended for SBS modified asphalt mixture in the high altitude and cold regions of the Tibetan Plateau. The splitting test is suitable for assessing low-temperature performance of asphalt mixtures in high altitude and cold regions with a loading rate adjusted to 2 mm/min. When the loading rate is adjusted to 10 mm/min, the beam bending test is suitable for studying the low-temperature performance of asphalt mixtures after long-term aging in high altitude and cold regions. The freezing and thawing split test is suitable for assessing low-temperature performance of asphalt mixtures after freezing and thawing in high altitude and cold regions when the loading rate is adjusted to 2 mm/min. Under long-term aging conditions, as temperature increases (−15°C∼0°C), the decay rate of maximum flexural-tensile strain of traditional asphalt mixture is bigger than that of SBS modified asphalt mixture. Having endured freezing and thawing cycles, the splitting strength and the maximum flexural-tensile strain of asphalt mixtures decreases. After 40 cycles of freezing and thawing, the maximum flexural-tensile strain decreases by 15.2% in comparison to state.