# Experimental Study of Low Temperature Performance of Porous Asphalt Mixture
## 3 Experimental Method and Results
### Influence Analysis of Factors
The modifier content is the most important factor affecting the low temperature performance of porous asphalt mixture. As can be seen from Figure 9, by increasing the modifier content from 9% to 15%, the flexural tensile strength decreased by 5.7%, the maximum bending strain increased by 18.5%, and the bending stiffness modulus decreased by 20.4%. The results demonstrate that SINOTPS modifier can significantly improve the deformation capacity and energy absorption capability of porous asphalt mixture, so that the porous asphalt mixture exhibits better low temperature performance. Figure 9: Influence of different levels of each factor on evaluation indicators. (**a**) Curves of flexural tensile strength; (**b**) Curves of maximum bending strain; (**c**) Curves of bending stiffness modulus. (3) Aging  
Aging has relatively little effect on the low temperature performance of porous asphalt mixture. The factors of porosity and aging are together the least and the second-least influential among the four factors. From Figure 9, it can be seen that the flexural tensile strength, maximum bending strain, and bending stiffness modulus of porous asphalt mixture with short-term aging are respectively 0.9%, 1.1%, and 0.5% lower compared to those of porous asphalt mixture with no aging. The flexural tensile strength and bending stiffness modulus of porous asphalt mixture with long-term aging are respectively 4.4% and 6.2% lower whereas the maximum bending strain is 0.4% higher, compared to those of porous asphalt mixture with no aging. The modest decrease in low temperature performance of porous asphalt mixture through aging was in line with the findings by [PERSON] et al. [45]. The slight effect of aging should be due to the effectiveness of the high viscosity SINOTPS modifier in improving the antiaging performance of porous asphalt mixture. (4) Test temperature  
The influence of test temperature on low temperature bending test results is less significant than that of modifier content. At this juncture, it is noteworthy that the brittle point is a threshold temperature of asphalt mixture at which its behaviour is transitioned from plastic to brittle. In low temperature bending test, in order to prevent possible sudden brittle fracture from affecting the accuracy of the results, the test temperature is generally set at higher than the brittle point temperature. For porous asphalt, the brittle point is lower than that of ordinary dense graded asphalt [57], and the test temperature can generally be set at \(-10\)\({}^{\circ}\)C to \(-20\)\({}^{\circ}\)C. Consequently, in order to investigate the effect of temperature changes on the low temperature performance of porous asphalt mixture, three levels of test temperature, namely \(0\)\({}^{\circ}\)C, \(-10\)\({}^{\circ}\)C, and \(-20\)\({}^{\circ}\)C, were adopted in the test. From Figure 9, it can be seen that when the test temperature was decreased from \(0\)\({}^{\circ}\)C to \(-20\)\({}^{\circ}\)C, the flexural tensile strength increased by 5.0%, the maximum bending strain decreased by 7.7%, and the bending stiffness modulus increased by 13.9%. The results indicated that in this temperature range, the porous asphalt mixture still exhibited plastic deformation, and the brittle point temperature was not reached [58]. The maximum bending strain decreased with the test temperature, indicating that the lower the test temperature, the less capable the porous asphalt mixture in resisting deformation. At the same time, the bending stiffness modulus of porous asphalt mixture increased with decreasing test temperature, indicating a reduction in the low temperature crack resistance of porous asphalt mixture.