Multi-index evaluation of cracking resistance of asphalt mixture in high altitude areas based on semi-circular bending tests

In western high altitude areas, strong ultraviolet radiation and high frequency freeze-thaw cycles and their coupling effects are the direct causes of asphalt concrete bridge pavement cracks. The purpose of this paper is to analyze the attenuation laws of cracking resistance of asphalt mixture under high altitude environment with multiple indices, and to propose a new comprehensive index. Firstly, laboratory tests were designed to simulate the aging effects of high altitude environment on asphalt mixture. Secondly, semi-circular bending (SCB) tests were used to investigate the performance attenuation of asphalt mixture under different coupling schemes. Finally, the monotonic relationship between each anti-cracking evaluation index and independent variables was explained by statistical analysis, and the cracking resistance index in high altitude region (HAR-CRI) was proposed. The results showed that the reduction of cracking resistance of asphalt mixture per unit of freeze-thaw cycle is 4.6 times higher than that of ultraviolet radiation, due to the surface property of ultraviolet aging; the maximum damage deepening values of Gf, RC, BCI, FEI, FI and CRI can reach 5.6 %, 7.6 %, 5.0 %, 4.3 %, 3.6 % and 2.0 % respectively, indicating that mutually deepening environmental factors had the greatest reduction in RC. According to correlation and difference analysis: FEI, RC and BCI were recommended to study the effects of temperature, freeze-thaw cycles frequency and ultraviolet radiation duration on cracking resistance of asphalt mixture respectively; ultraviolet radiation duration only had significant effects on FI and CRI in the three-factor interaction. Based on the principal component analysis, a comprehensive index (HAR-CRI) covering more than 98 % of multiple-index information was proposed. It can effectively reflect the strength properties of materials, and can be used to predict and rank the cracking resistance of asphalt mixtures under different environmental conditions in high altitude areas. •FEI, RC and BCI were recommended to study the effects of temperature, freeze-thaw cycles frequency and ultraviolet radiation duration.•Mutually deepening environmental factors had the greatest reduction in RC.•A new SCB index (HAR-CRI) was established through statistical analysis.•HAR-CRI can predict and rank the cracking resistance of asphalt mixture.