## 2 Materials and Methods
### Test Methods
#### 2.3.3. Fiber-Asphalt Pulling Test  
The fiber-asphalt pulling machine (Figure 4) was designed by Yangzhou University, China. The test parameters were controlled by a control panel (Figure 5), and different test parameters such as test temperature, pulling speed can be edited through this control panel. The temperature range of this instrument is 10 \({}^{\circ}\)C to 80 \({}^{\circ}\)C, the capacity of the load cell is 30 N, the sampling rate is 2 times per second, and the minimum unit of the displacement sensor is 1 mm. According to the previous research of this instrument [20], the test data was the stablest (the variation of the test data was the lowest) when the test temperature was 40 \({}^{\circ}\)C, the pulling speed was 10 mm/min and the length of the fiber being buried into the asphalt mortar was 20 mm. In order to make the test data more reliable, the test will be conducted three times under the same test parameters, and the test will be re-conducted when the deviation between the test result of a single test and the average value was more than 10%. The average value was adopted as the final test results of the pulling force. Figure 4: Fiber-asphalt pulling machine. Figure 5: Control panel. The process of the test was listed as follows: (1) Pour the asphalt mortar into the separate part of the mold to the half of its height (Figure 6a). (2) Make a mark at the fiber 20 mm away from the end of the fiber, put the continuous fiber into the asphalt mortar, and put two small pieces of paper onto the surface of the surface of the gap in the mold (Figure 6b). (3) Pour the rest of the asphalt mortar into the mold and make it cool at room temperature to prepare the test (Figure 6c). (4) Put the mold into the chamber of the instrument (Figure 6d), and adjust the location of the fixer of the fiber (marked by the red arrow) to make it parallel to the length direction of the fiber, and fix the fiber on the fixer by wrapping the fiber around the fixer. (5) Close the chamber and set the temperature as 40 \({}^{\circ}\)C to heat the specimen at 40 \({}^{\circ}\)C for 1 h. (6) Record the maximum pulling force in the test and using the nominal bonding stress calculation equation to calculate the NBS index. The continuous basalt fiber consists of 400 single basalt fibers with the diameter of 16 \(\upmu\)m or 17 \(\upmu\)m, considering the two kinds of continuous basalt fibers used in this paper. As it can be seen from Figure 7, the asphalt mortar does not fully soak into the fiber. This phenomenon can be explained in two ways. Firstly, in the sample preparation process, the outer side of the asphalt mortar sample will get cold first, which could create the temperature stress inside the asphalt mortar sample. The direction of the temperature stress was from the inner side to the outer side, because the outer side will get cold first. The draft of the distribution of the temperature stress is illustrated in Figure 8, and this temperature stress could induce the inner stress expanding from inside the fiber (as is shown in Figure 7). The main causes of this stress were the temperature difference and the shrinkage and expansion of the asphalt mortar caused by it. Secondly, the 400 single micron level basalt fibers overlay with each other and they were connected and touched with each other by the coupling agent on the surface of the single tiny fibers. Therefore, the distribution of asphalt mortar inside the fiber was also affected by the blocking effect of the overlaying of the micron level fibers. The temperature force will disappear when the sample as a whole reaches the room temperature. At the same time, the distribution of the asphalt mortar inside the fiber is fixed until conducting the pulling test. Figure 6: Continuous basalt fiber: (**a**) Step 1; (**b**) Step 2; (**c**) Step 3; (**d**) Step 4. Figure 7: Analysis of the asphalt distribution inside the fiber.