# Analysis of the Odor Purification Mechanism and Smoke Release of Warm-Mixed Rubber Asphalt
## 3 Results and Discussion
### Analysis of Asphalt Smoke Composition
#### 3.5.3 Sulfur Dioxide  
From Figure 7a, it can be seen that there are differences in the degradation effects of sulfur dioxide among the three types of asphalt, namely matrix asphalt NA, rubber asphalt AR, and warm-mix rubber asphalt WMAR. The sulfur dioxide concentrations generated by the three types of asphalt during the experimental process are 0.155 mg/m\({}^{3}\), 0.284 mg/m\({}^{3}\), and 0.238 mg/m\({}^{3}\), respectively. The matrix asphalt has the most significant degradation effect on sulfur dioxide, indicating that during the process of asphalt modification, the degradation degree of sulfur dioxide by modified asphalt has decreased. During the process of asphalt modification, rubber asphalt AR and warm-mix pure odor asphalt WMAR contain higher levels of VOCs, so more harmful gases are emitted during heating, and the degradation degree of nitrogen oxides by modified asphalt is reduced. When adding new materials or warm-mix agents, modified asphalt may undergo chemical reactions, which may lead to an increase in the content of VOCs in the asphalt. The experiment was conducted by adding rubber asphalt AR and warm-mix clean-odor asphalt WMAR to liquid odor agent and powder odor agent with proposed concentrations of 0%, 0.2%, 0.4%, and 0.6%. The experimental results showed that the modified asphalt with added odor agent reduced the concentration of sulfur dioxide produced to varying degrees in the experiment, and the degradation effect was better.  
In Figure 7b, it can be seen that for liquid deodorant (LD), when the proposed deodorant dosage is 0%, 0.2%, 0.4%, and 0.6%, the sulfur dioxide concentration generated by the purified rubber asphalt DAR in the experiment is 0.284 mg/m\({}^{3}\), 0.152 mg/m\({}^{3}\), 0.091 mg/m\({}^{3}\), and 0.073 mg/m\({}^{3}\), respectively. The degradation rate is 74.2%. The sulfur dioxide concentrations generated by DWMAR, a clean and warm-mixed rubber asphalt, in the experiment are 0.238 mg/m\({}^{3}\), 0.124 mg/m\({}^{3}\), 0.072 mg/m\({}^{3}\), and 0.065 mg/m\({}^{3}\), respectively. The degradation rate is 72.6%. For PD odor remover, when the proposed dosage of odor remover is 0%, 0.2%, 0.4%, and 0.6%, the sulfur dioxide concentration generated by DAR in the experiment is 0.284 mg/m\({}^{3}\), 0.113 mg/m\({}^{3}\), 0.071 mg/m\({}^{3}\), and 0.057 mg/m\({}^{3}\), respectively. The degradation rate is 79.9%. The sulfur dioxide concentrations generated by DWMAR, a clean and warm-mixed rubber asphalt, in the experiment are 0.238 mg/m\({}^{3}\), 0.089 mg/m\({}^{3}\), 0.063 mg/m\({}^{3}\), and 0.052 mg/m\({}^{3}\), respectively. The degradation rate is 78.1%, indicating that for the same type of deodorizer, an increase in the dosage of the deodorizer leads to a decrease in the concentration of sulfur dioxide and a better degradation effect. When adding the same type and concentration of deodorizing agents, the degradation rate of sulfur dioxide by DWMAR is lower than that of DAR, indicating that the coupling effect of warm-mixing agents and deodorizing agents may reduce the degradation rate of sulfur dioxide or produce sulfur dioxide in the reaction. In addition, the line chart shows that adding the same concentration of odor remover to the same type of asphalt results in a better degradation effect when powder odor remover is added.