# Laboratory Performance Evaluation of Hot-Mix
## 4 Test Procedures  
Based on the HMAs listed in Table 3, the high- and low-temperature, fatigue, and dynamic modulus properties of the mixtures designed by different variable combinations were evaluated using different tests. The uniaxial penetration shear test (UPST) and unconfined compression test (UCT) were chosen to analyze HMA high-temperature performance. The specimens of above tests had diameters of 100 mm and heights of 100 mm, and they were formed by gyratory compactor. The low-temperature bending test (LTBT) was used to evaluate the HMA low-temperature performance. The specimens for bending test, which were formed using rolling wheel compactor, had dimensions of 250 mm \(\times\) 30 mm \(\times\) 35 mm. The four-point bending fatigue test (4 PBT) was applied to assess the HMA fatigue property. The corresponding specimens had dimensions of 380 mm \(\times\) 50 mm \(\times\) 63 mm and were formed by vibrating compactor. The uniaxial compressive modulus test (UCMT) was used to measure the HMA dynamic modulus. The specimens for the dynamic modulus test were prepared by gyratory compactor, and had diameters of 100 mm and heights of 150 mm. In addition, the detailed tests arranged for different groups of HMAs are summarized in Table 4.  
The UPST reflects the shear strength of HMA at high temperature (60 \({}^{\circ}\)C) [15; 16; 17]. The experimental device of UPST is presented in Figure 2a. During the experiment, an indenter with a diameter of 28.5 mm was loaded on the asphalt mixtures at a rate of 1 mm/min. The maximum force was recorded to calculate the shear strength of asphalt mixtures, as shown in Equation (1) [18]. \[R_{\tau}=f_{\tau}\cdot\frac{P}{A} \tag{1}\]  
where \(R_{\tau}\) is shear strength (MPa); \(P\) is the maximum force (N); \(A\) is the contact area of indenter (mm\({}^{2}\)); and \(f_{\tau}\) is the correction factor (i.e.,\(f_{\tau}\) = 0.34). The UCT mainly reflects the compressive strength of HMA at high temperature (60 \({}^{\circ}\)C). The experimental device of UCT is presented in Figure 2b. In contrast to UPST, the surface of asphalt mixtures in UCT was subjected to uniform indenter load, and the loading rate was controlled at 1 mm/min. During the process, the maximum force was recorded to calculate the compressive strength of asphalt mixtures [13]. The LTBT characterizes the tenacity of asphalt mixtures at low temperature (\(-\)10 \({}^{\circ}\)C). The experimental device of LTBT is presented in Figure 2c. During the experiment, the load was applied to the midspan of rectangular asphalt mixtures, and the loading rate was controlled at 50 mm/min. The deflection of the midspan d corresponding to the maximum force was recorded. Then, the \begin{table}
\begin{tabular}{c c c c c} \hline
**Experiments** & **UCT** & **UPST** & **LTBT** & **4 PBT** & **UCMT** \\ \hline Group 1 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 2 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 3 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 4 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 5 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 6 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Group 7 & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ \hline \end{tabular}
\end{table} 
Table 4: The detailed tests arranged for different groups of HMAs. flexural-tensile strain \(\varepsilon_{\text{B}}\) of asphalt mixtures at failure was calculated according to the following Equation [13]. \[\varepsilon_{B}=\frac{6\times h\times d}{L^{2}} \tag{2}\]  
where \(\varepsilon_{B}\) is the flexural-tensile strain at low temperature(\(\mu\varepsilon\)); \(L\) is the span of beam (mm); \(h\) is the height of midspan (mm); and \(d\) is the deflection of midspan in failure (mm). The four-point bending test (4 PBT) was used to characterize the fatigue life of asphalt mixtures [10]. The experimental device of FPBT is presented in Figure 2d.