# Experimental Study of Low Temperature Performance of Porous Asphalt Mixture
###### Abstract
[21] proposed a new open-graded porous asphalt mixture that used epoxy asphalt as the binder to improve the pavement durability, and the results showed superior overall performance of the epoxy modified open-graded porous asphalt mix compared to conventional open-graded porous asphalt mixes. [PERSON] and [PERSON] [22] conducted an experimental study and performance evaluation of small particle porous epoxy asphalt mixture, and the mixture was designed with the aid of a binder drainage test and a raveling test. They found that the proposed porous epoxy asphalt mixture had good mechanical properties while retaining satisfactory frictional resistance and permeability. [PERSON] and [PERSON] [23] applied the Coarse Aggregate Void Filling (CAVF) method to the mix proportions design of porous asphalt, and proposed the method to determine the optimum compaction temperature of porous asphalt mixture. Although the porous asphalt has many advantages, there are also some drawbacks in its application. The low temperature cracking problem of asphalt pavement is reported to be prominent in some cold regions [24; 25; 26; 27]. Survey results showed that more than one third of the damages of porous asphalt in cold regions were attributed to its inferior low temperature cracking resistance performance [28]. Asphal mixture has the characteristics of stress relaxation. When the ambient temperature decreases slowly, the tensile stresses in asphalt mixture caused by temperature drop that accumulate gradually with time would be relieved by relaxation and would not reach the ultimate tensile stress level to cause cracking. On the other hand, the thermal contraction cracks of asphalt mixture often occur in extreme weather where the temperature descends rapidly, such as that caused by an acute cold current or cold wave. In such weather condition, the tensile stresses induced in asphalt mixture accumulate at a faster rate than the relaxation, so that cracks would appear when the ultimate tensile stress level is attained. It should be noted that for porous asphalt pavement in cold regions, in addition to the cracks caused by the ambient temperature reduction, the fluctuation of ambient temperature around the freezing point will cause the water trapped inside internal voids to undergo freeze and thaw and induce damages [29; 30; 31]. Porous asphalt pavement is more susceptible to freeze-thaw cycles in winter compared to ordinary dense gradation asphalt pavement [32]. Therefore, porous asphalt pavement used in cold regions should be designed to have excellent low temperature performance. At present, research on porous asphalt has focused on various aspects including moisture susceptibility [2; 22], fatigue resistance and healing effect [33], material optimization [34; 35; 36], filtration characteristics [37], rutting resistance [22; 38], ravelling resistance [39], and noise reduction characteristics upon siltation [40]. However, research on low temperature performance of porous asphalt mixture is relatively in lack [41]. [PERSON] and [PERSON] [42] studied the relationship between low temperature cracking and aging performance of asphalt mixture and highlighted the importance of the appropriate use of modifier. [PERSON] et al. [43] found that the incorporation of ethylene bis stearic acid amide (EBS) and stearic acid amide (SA) could improve the low temperature deformability, reduce the failure stiffness modulus, and improve the low temperature crack resistance of warm-mixed porous asphalt mixture. [PERSON] et al. [44] explored the feasibility of the application of porous asphalt mixture with steel slag for seasonal frozen regions, and ascertained the optimal replacement percentage of natural aggregate. In their test, steel slag coarse aggregate was used to replace basalt coarse aggregate at four levels (25%, 50%, 75%, 100%) by equal volume, and the results indicated that the low temperature cracking resistance of the mixture was significantly enhanced and acoustic emission energy was uniformly released by the incorporation of steel slag.