# Mechanism of HCB-Modified Asphalt and Dynamic Properties of Mixtures
## 3 Test Methods
### SPT of HCB-Modified Asphalt Mixture  
In this experiment, \(\varphi\)150 mm \(\times\) H 150 mm cylinders prepared in the Troxler 4140 gyratory compactor were cored and cut to obtain \(\varphi\)100 mm \(\times\) H 110 mm specimens. Dynamic moduli and phase angle tests are measured by Simple Performance Test (SPT ). The stress corresponding to 50-150 microstrain was taken by sine wave. Three parallel tests were conducted to reduce discrepancy. Referring to test conditions of previous research, the test temperatures were 4.4 \({}^{\circ}\)C, 21.1 \({}^{\circ}\)C, 37.8 \({}^{\circ}\)C, and 54.4 \({}^{\circ}\)C with the respective load frequencies of 0.1 Hz, 0.5 Hz, 1 Hz, 5 Hz, 10 Hz, and 25 Hz. SPT equipment and specimen are exhibited in Figures 1 and 2, respectively. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Mxture** & **16** & **13.2** & **9.5** & **4.75** & **2.36** & **1.18** & **0.6** & **0.3** & **0.15** & **0.075** \\
**mm** & **mm** & **mm** & **mm** & **mm** & **mm** & **mm** & **mm** & **mm** & **mm** \\ \hline AC-13 & 100 & 95.6 & 72.7 & 40.4 & 30 & 19.4 & 14.5 & 10.3 & 8.1 & 5.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mixture gradation. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Asphalt Mixture** & **Optimal** & **Volume of** & **Voids in** & **Voids filled** & **Marshall** & **Flow** \\
**Asphalt** & **Asphalt** & **Air Voids** & **Mineral** & **with** & **Stability** & **Value** \\
**Comment (\%)** & **(\%)** & **(\%)** & **Aggregate (\%)** & **Asphalt (\%)** & **(kN)** & **(mm)** \\ \hline BAM & 4.5 & 3.95 & 14.5 & 72.8 & 12.5 & 3.1 \\ HAM & 4.5 & 4.18 & 14.4 & 72.3 & 13.4 & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameters of asphalt mixture for the Marshall design method. Figure 3 shows that CB particles were mostly ellipsoidal aggregates and the surface was rough, while the surface of HCB was smoother than that of CB. In addition, its shape was irregular and the floc was apparently reduced. Due to the different degree of polymerization, the particle size of the HCB varied, and the average particle size was between 5 and 100 \(\upmu\)m. These characteristics gave HCB higher surface energy and larger intermolecular forces, and the interaction between particles and asphalt was stronger. As illustrated in Figure 4, the infrared spectra of CB and HCB had some similar characteristics. The absorption bands of C-H overtone absorption and C=C in-plane deformation vibration appeared at approximately 1654 cm\({}^{-1}\), but the absorption intensity was weak; the Si-O absorbance band appeared at 1375 cm\({}^{-1}\), and the C-O absorbance bands appeared at 1063 cm\({}^{-1}\),1013 cm\({}^{-1}\), and 975 cm\({}^{-1}\). The infrared spectrum of CB showed no absorption peak near 3500 cm\({}^{-1}\). However, the broad and strong characteristic absorption peak at 3446 cm\({}^{-1}\) corresponded to the stretching vibration of O-H in the infrared spectrum of HCB. The peak was sharp and there was no interference from other absorption peaks, indicating the generation of the hydroxyl group. The hydroxyl groups on the surface of HCB combined with the carbonyl group in the asphalt to form hydrogen bonds, which can affect the properties of asphalt. Based on Figure 5, CB and HCB contain C, Si, O, and Au elements. The Si element was an impurity contained in the specimen materials, and the Au element was introduced when the specimen materials  
Figure 4: The infrared spectra of CB and HCB. Figure 5: The X-ray diffraction spectra of (**a**) CB and (**b**) HCB. were sprayed with gold. This investigation chose Au as the internal reference element to calculate the oxygen content. The oxygen content of CB was 13.62%, and the oxygen content of HCB was higher than that of CB, reaching 24.78%. It is generally believed that the higher the oxygen content, the more active the surface chemical properties of carbon black. HCB contains CH, C=C, Si-O, and CO, and has a high oxygen content, so HCB can react with cycloalkanes and paraffins in asphalt to form chemical bonds.