# Experimental Study of Low Temperature Performance of Porous Asphalt Mixture
## 4 Conclusions  
In this paper, the low temperature performance of porous asphalt mixture has been studied through the low temperature bending test. The following major conclusions can be drawn:  
(1) Through orthogonal experimental design, four main factors affecting the low temperature performance of porous asphalt mixture have been analyzed. The results revealed that the descending order of influence of factors on flexural tensile strength of porous asphalt mixture was: modifier content, test temperature, aging condition, and porosity. The descending order of influence of factors on maximum bending strain was: modifier content, test temperature, porosity, and aging condition; and the descending order of influence of factors on bending stiffness modulus was: modifier content, test temperature, aging condition, and porosity. (2) The modifier content was the most important factor affecting the low temperature performance of porous asphalt mixture, followed by test temperature. By increasing the modifier content from 9% to 15%, the flexural tensile strength decreased by 5.7%,  
Figure 10: Relationship between maximum bending strain and porosity. the maximum bending strain increased by 18.5%, and the bending stiffness modulus decreased by 20.4%. The results demonstrated that SINOTPS modifier could significantly improve the deformation capacity and energy absorption capability of porous asphalt mixture. By decreasing the test temperature 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 the lower the test temperature, the less capable the porous asphalt mixture in resisting deformation, and the poorer the low temperature crack resistance of porous asphalt mixture. (3) The factors of porosity and aging were the least and the second-least influential among the four factors. The porosity affected the three low temperature performance evaluation indicators, but the effect was limited to within 4% when the porosity increased from 16.2% to 23.8%. Compared with porous asphalt mixture with no aging, the flexural tensile strength and bending stiffness modulus of porous asphalt mixture with long-term aging were respectively 4.4% and 6.2% lower, whereas the maximum bending strain was 0.4% higher. The slight effect of aging should be due to the effectiveness of the SINOTPS modifier in improving the anti-aging performance of porous asphalt mixture. (4) The orthogonal test results revealed that the maximum bending strain had the highest sensitivity to porosity among the three performance evaluation indicators, namely the flexural tensile strength, maximum bending strain, and bending stiffness modulus. The effect of porosity on low temperature performance of porous asphalt mixture has been further examined through the single factor influence test. The results showed that there existed an approximately linear correlation between the maximum bending strain and the porosity of porous asphalt mixture, and the maximum bending strain decreased with increasing porosity. Furthermore, when designing the mix proportions of porous asphalt mixture, to ensure good working performance of porous asphalt mixture in low temperature environment, the porosity should also satisfy the limit requirements of the maximum bending strain in relevant technical standards. Further research on the low temperature performance of the porous asphalt mixture containing recycled asphalt materials is recommended. Conceptualization, J.W. and Y.G. ; methodology, Y.G. ; formal analysis, J.W. and Y.G. ; investigation, J.W., P.-L.N. and Y.G. ; resources, P.-L.N. and Y.G. ; data curation, [PERSON]; visualization, [PERSON]; validation, H.S. and J.D. ; writing--original draft preparation, [PERSON], P.-L.N. and Y.G. ; writing--review and editing, [PERSON], P.-L.N. and H.S. ; project administration, [PERSON]; supervision, J.D. ; funding acquisition, P.-L.N. and J.D.