## 9 Thermal Properties of Asphalt Mixture Components
### Specific Heat Capacities of Asphalt Mortars and Aggregates  
As shown in Table 2, the specific heat capacity and thermal conductivity of aggregate and asphalt mortar vary with temperature. Considering specific heat capacity first, the specific heat capacities of asphalt, aggregate and mineral powder were measured by [PERSON] et al. [34], as Table 3 shows. It can be found that the specific heat capacities of aggregate and mineral powder in asphalt mixture have a strict linear correlation with temperature, and the relationship between asphalt and temperature has a quasi-linear correlation. The specific heat capacity of aggregate was used directly in this study, but asphalt mortar contains asphalt, fine aggregate and mineral powder. At present, there is no related research to directly measure the specific heat capacity of asphalt mortar. According to the existing research achievements [35], the specific heat capacity of multiphase composites can be calculated according to the following formula:  
\[C=\frac{\sum\limits_{i=1}^{n}m_{i}C_{i}}{M}=\sum\limits_{i=1}^{n}p_{i}C_{i} \tag{7}\]  
where \(C\) is the specific heat capacity of composite, \(M\) is the mass of composites, \(m_{i}\) is the mass of each component, \(C_{i}\) is the thermal conductivity of each component, \(n\) is the number of components and \(p_{i}\) is the mass percentage of each component. According to the aggregate gradations and asphalt contents of the asphalt mixtures shown in Table 1, the mass contents of each component in asphalt mortars can be calculated, as shown in Figure 5. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Thermal Property**} & \multicolumn{2}{c}{**Symbols and Units**} & \multirow{2}{*}{**Asphalt Mortar**} & \multirow{2}{*}{**Aggregate**} & \multirow{2}{*}{**Air Void**} \\ \hline Conductivity & \(k(\mathrm{J}/(\mathrm{mm}\cdot\mathrm{h}\cdot\mathrm{c}))\) & vary with temperature & vary with temperature & 0.0828 \\ Density & \(\rho\left(\mathrm{kg}/\mathrm{mm}^{3}\right)\) & \(1.05\times 10^{-6}\) & \(2.8\times 10^{-6}\) & \(1.225\times 10^{-9}\) \\ Specific heat capacity & \(C(\mathrm{J}/(\mathrm{kg}\cdot\mathrm{c}))\) & vary with temperature & vary with temperature & 1.005 \\ Pavament surface & \(\varepsilon\) & 0.81 & 0.81 & - \\ emissivity & \(h_{c}\left(\mathrm{J}/\left(\mathrm{mm}^{2}\cdot\mathrm{h}\cdot\mathrm{c}\right)\right)\) & \(2.4466\times 10^{-2}\) & \(9.2048\times 10^{-2}\) & - \\ Absolute temperature zero & \(T_{Z}(\mathrm{c}^{\mathrm{C}})\) & & \(-273\) & \\ Stefan–Boltzmann constant & \(\sigma\left(\mathrm{J}/\left(h\cdot\mathrm{mm}^{2}\cdot\mathrm{c}^{4}\right)\right)\) & & \(2.041092\times 10^{-10}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Thermal properties of asphalt mixture components. According to the mass contents of each component shown in Figure 5 and the specific heat capacity at different temperatures of each component in Table 3, the asphalt mortar specific heat capacity variation law with temperature can be obtained, as shown in Figure 6. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Temperature (\({}^{\circ}\)C)**} & \multicolumn{3}{c}{**Specific Heat (J/kg.*C)**} \\ \cline{2-4}  & **Asphalt** & **Aggregate** & **Mineral Filler** \\ \hline
0 & 1583 & 808 & 803 \\
10 & 1633 & 820 & 822 \\
20 & 1706 & 831 & 844 \\
25 & 1725 & 837 & 852 \\
30 & 1707 & 843 & 861 \\
35 & 1723 & 850 & 871 \\
40 & 1758 & 855 & 879 \\
45 & 1829 & 862 & 890 \\
50 & 1865 & 868 & 899 \\
55 & 1863 & 873 & 910 \\
60 & 1870 & 880 & 920 \\
65 & 1904 & 886 & 930 \\
70 & 1938 & 891 & 939 \\
75 & 1976 & 896 & 950 \\
80 & 1967 & 902 & 960 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specific heat capacities of asphalt mixture components at different temperatures. Figure 5: Mass contents of components in asphalt mortars. Figure 6: Specific heat capacity variations with the temperature of asphalt mortar.