## 3 Results
### Analysis of Hot Recycled Mixture Based on CAM Model  
#### 3.4.1 Dynamic Characteristics  
As a typical viscoelastic material, an asphalt mixture has significant temperature sensitivity. According to the time-temperature superposition principle [27], the mechanical phenomena of these mixtures at different temperatures can be translated to obtain the mechanical properties at a wider range of temperatures and frequencies. In this paper, the improved CAM model was used to analyze the dynamic viscoelastic characteristics of the reclaimed asphalt mixture [28], in which the dynamic modulus and phase angle were expressed as follows:  
\[|G^{*}|=G^{*}_{e}+\frac{G^{*}_{g}-G^{*}_{e}}{\left[1+\left(f_{c}f^{\prime} \right)^{k}\right]^{m_{e}/k}} \tag{2}\]  
where \(G^{*}_{e}\) is the complex shear modulus of the equilibrium state; \(G^{*}_{g}\) is the glassy complex shear modulus; \(f_{c}\) is the elastic limit threshold; and \(k\) and \(m_{e}\) are shape parameters and rheological parameters, respectively. \(R\) is the intercept of \(G^{*}_{e}\) and \(G^{*}_{g}\) on logarithmic coordinates, which can be calculated as follows:  
\[R=\lg\frac{2^{m/k}}{1+\left(2^{m/k}-1\right)G^{*}_{e}/G^{*}_{g}} \tag{3}\]  
\[\delta=\delta_{m}\left[1+\left(\frac{\log(f_{d}/f^{\prime})}{R_{d}}\right)^{2 }\right]^{-m_{d}/2} \tag{4}\]  
where \(\delta_{m}\) is the maximum phase angle of the viscous component of the mixture; \(f_{d}\) is the frequency corresponding to the highest point of the phase angle; and \(R_{d}\) is the shape parameter. Taking 20 \({}^{\circ}\)C as the reference temperature, the least square method was used to plan and solve the problem. After translating the other three temperatures, the improved CAM model was adopted to carry out a fitting analysis on the dynamic moduli of the three mixtures. The main curve of the dynamic moduli of asphalt mixtures was drawn, as shown in Figure 8.  
The dynamic modulus master curve fitting parameters are shown in Table 6, where it can be seen that when a vehicle's driving speed is about 60 km/h, the loading frequency is equivalent to 10 Hz. When the loading frequency is greater than 10 Hz, the dynamic modulus of the three asphalt mixtures is RAP > RAP + PCO > RAP + WPO, and high frequency corresponds to low temperature, which indicates that the addition of two regenerators reduces the dynamic modulus of the asphalt mixture at low temperature, so it is easier to produce deformation and release temperature stress. This is also proved by the fitting results of the CAM model, whose fitting parameter fc reflects the frequency of the same viscous and elastic components of the asphalt mixture, and the higher the fc, the better the anti-cracking performance at low temperature. When the loading frequency is less than 0.01 Hz, the dynamic moduli of the three asphalt mixtures are RAP > RAP + WPO > RAP + PCO, and the low frequency corresponds to the high temperature. The addition of the regenerating agent reduces the viscosity of the asphalt binder, thus reducing the high-temperature stability of the asphalt mixture. The \(m_{e}\) and \(R_{d}\) of the fitting parameters reflect the temperature sensitivity of the mixture. The lower \(m_{e}\) and \(R_{d}\) are, the less sensitive the mixture is to temperature. The fitting results of \(m_{e}\) and \(R\) are RAP > RAP + PCO > RAP + WPO, which indicates that the temperature sensitivity of the waste-palm-oil-based reclaimed asphalt mixture is better than that of the petrochemical-oil-based reclaimed asphalt mixture, while the RAP has the worst temperature sensitivity. The phase angle is an important parameter reflecting the viscoelastic properties of asphalt mixtures, which represents the change in the viscoelastic ratio of an asphalt mixture. The higher the phase angle is, the greater the viscous component is.