## 1 Introduction
The microstructure and strengthening mechanism of basalt fiber was also studied by scanning electron microscopy. The results showed the basalt fiber can obviously improve the crack resistance of asphalt mast than other fibers [12]. [PERSON] et al. found that basalt fiber could significantly improve the tensile strength of asphalt mixture [13]. [PERSON] et al. studied the low-temperature performance of asphalt mixture under salt freeze-thaw cycles with low-temperature bending experiments. The results showed that the concentration of the salt solution and freeze-thaw temperature had significant influence on the low-temperature performance of mixture. Basalt fiber improved the low-temperature performance of mixture under salt freeze-thaw cycles [14]. [PERSON] et al. evaluated the fatigue life of basalt fiber and diatomic composite modified asphalt with four-point bending beam experiment, and the experimental results showed that basalt fiber improved the low-temperature performance of asphalt mixture [15]. [PERSON] et al. studied the performance of basalt modified asphalt mixture under the coupling effect of chloride erosion and freeze-thaw cycles. It was found that basalt fiber greatly improved the low-temperature bending and fatigue performances of asphalt mixture [16]. In addition, basalt fiber could improve the resistance and pavement performance of asphalt road under complex environment. [PERSON] et al. studied the performance improvement of asphalt mixtures modified with different modifiers at different salt concentrations and different environments. The test results showed that basalt fiber had the best improvement on mechanical properties of asphalt mixtures under salty and humid environment [17; 18]. [PERSON] et al. studied the performances of basalt fiber modified asphalt mixture as the surface layer of bus lane pavement, and found that basalt fiber modified asphalt had good performance in resisting permanent deformation and increasing road friction [19]. The raw material cost of basalt fiber modified asphalt pavement has increased by 15-20%, but the service life of the pavement can increase by 30-40% [20; 21]. From what has been discussed above, basalt fiber is suitable to be used as a modified material for asphalt pavement in northeast China. The asphalt concrete pavement in northeast China faces the freeze-thaw cycles conditions. The freeze-thaw cycles had a great threat to the durability of asphalt pavement. Many researchers analyzed the mechanism of freeze-thaw damage of asphalt mixture, in general, the water permeated and remained in the pores of the pavement, when the external temperature decreased, the pore water froze and volume expanded, which resulted in the generation of frost heave. When the temperature increased, ice melted into water and began the next freeze-thaw cycle. With repeated freeze-thaw cycle, the internal pore morphology and bituminous viscosity of the mixture were significantly changed and the performances of the mixture were significantly reduced [22; 23; 24; 25]. In order to more vividly reflect the mechanism of freeze-thaw damage of asphalt mixture, research focused on the performance changes of asphalt mixture under freeze-thaw cycles through macroscopic test or mesoscopic analysis. [PERSON] et al. studied the micro-thermodynamic behavior of asphalt mixtures under a freeze-thaw cycle with information entropy theory, X-ray tomography and image processing technology [26]. [PERSON] performed the freeze-thaw aging test and carried out Fourier transform infrared spectroscopy quantitative to analyze the compositions and rheological properties of asphalt mixture in cold regions [27]. [PERSON] et al. studied the internal evolution and analyzed the pore distribution changes and permeability of asphalt mixture during a freeze-thaw cycle with X-ray tomography [28; 29]. [PERSON] et al. analyzed the pore structure of semi-rigid base materials under freeze-thaw cycles with X-ray tomography [30]. [PERSON] et al. established the performance decay model of asphalt pavement in cold regions.