# Analysis of the Odor Purification Mechanism and Smoke Release of Warm-Mixed Rubber Asphalt
## 3 Results and Discussion
### Analysis of Asphalt Smoke Composition
#### 3.5.2 Nitrogen Oxides  
According to Figure 6a, it can be seen that there are differences in the degradation effects of nitrogen oxides among the three types of asphalt for matrix asphalt NA, rubber asphalt AR, and warm-mix rubber asphalt WMAR. The nitrogen oxide concentrations generated by the three types of asphalt during the experimental process are 0.681 mg/m\({}^{3}\), 0.812 mg/m\({}^{3}\), and 0.723 mg/m\({}^{3}\), respectively. Among them, the matrix asphalt has the most significant degradation effect on nitrogen oxides, indicating that during the process of asphalt modification, the degradation degree of nitrogen oxides 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 liquid (LD) and powder (PD) purifiers with proposed concentrations of 0%, 0.2%, 0.4%, and 0.6% to rubber asphalt AR and warm-mix pure-odor asphalt WMAR. The results of the experiments are summarized in Table 1.  
Figure 5: Ammonia analysis.  
mix clean-odor asphalt WMAR. The experimental results showed that the modified asphalt with added purifiers reduced the concentration of nitrogen oxides produced to varying degrees in the experiment and had better degradation effects.  
In Figure (b)b, it can be seen that for liquid deodorant (LD), when the proposed deodorant dosage is 0%, 0.2%, 0.4%, and 0.6%, the nitrogen oxide concentrations generated by the purified rubber asphalt DAR in the experiment are 0.812 mg/m\({}^{3}\), 0.452 mg/m\({}^{3}\), 0.391 mg/m\({}^{3}\), and 0.333 mg/m\({}^{3}\), respectively. The degradation rate is 58.9%. The nitrogen oxide concentrations generated by DWMAR, a clean and warm-mixed rubber asphalt, in the experiment are 0.723 mg/m\({}^{3}\), 0.397 mg/m\({}^{3}\), 0.31 mg/m\({}^{3}\), and 0.273 mg/m\({}^{3}\), respectively. The degradation rate is 62.2%. For PD odor remover, when the proposed dosage of odor remover is 0%, 0.2%, 0.4%, and 0.6%, the nitrogen oxide concentrations generated by purified rubber asphalt DAR in the experiment are 0.812 mg/m\({}^{3}\), 0.425 mg/m\({}^{3}\), 0.333 mg/m\({}^{3}\), and 0.292 mg/m\({}^{3}\), respectively. The degradation rate is 64.0%. The nitrogen oxide concentrations generated by DWMAR, a clean and warm-mixed rubber asphalt, in the experiment are 0.723 mg/m\({}^{3}\), 0.366 mg/m\({}^{3}\), 0.311 mg/m\({}^{3}\), and 0.232 mg/m\({}^{3}\), respectively. The degradation rate is 67.9%. This indicates that for the same type of deodorizer, an increase in the dosage of the deodorizer results in a decrease in the concentration of nitrogen oxides and a better  
Figure 6: Nitrogen oxide analysis.  
degradation effect. When adding the same type and concentration of odor-clarifying agents, the degradation rate of nitrogen oxides in DWMAR with clean and warm-mixed rubber asphalt is higher, indicating that the coupling effect of temperature mixing agents and odor-purifying agents may increase the degradation rate of nitrogen oxides. 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 (PD) is added.