# Laboratory Evaluation of Wear Particle Emissions and
## 3 Results  
### Analysis of TRWPs for PSMA Mixtures  
The analysis of TRWPs was conducted in two stages. In the first stage, the wear particles suspended during the test were measured by their cumulative number (particle count) and average PM mass concentrations using a real-time measurement sensor to analyze the wear particle generation trend. In the second stage, given that all wear particles generated during the experiment were accumulated at the bottom of the chamber, they were collected after the test was completed. The collected wear particles were recorded as TRWP emissions (g) and analyzed. Figure 7 plots the trend of dust generated over time to determine the LTWRP test time. In the graph shown in this figure, the \(x\)-axis denotes the test time, while the \(y\)-axis denotes the cumulative number of wear particles. As this cumulative number is extremely large, it was expressed as an exponent. During the initial 100 h, the slope of the number of dust particles generated varied. However, after 100 h, the slope tended to remain constant. In this study, the test was conducted for 100 h to evaluate the number of wear particles generated according to the maximum aggregate size of the asphalt mixture. Therefore, the cylindrical specimen was tested for 100 h at a speed of 40 km/h after applying the load of the tires, thereby simulating a total of 4000 km of road driving. Table 3 shows the results of the test conducted on the suspended dust concentrations (\(\mathrm{\SIUnitSymbolMicro g/m^{3}}\)) and TRWP emissions (g) for different NMASs of the PSMA mixtures. In Table 3, the suspended dust concentration was categorized into PM\({}_{0.3}\), PM\({}_{0.5}\), PM\({}_{1}\), PM\({}_{2}\), PM\({}_{5}\), and PM\({}_{10}\) based on the PM size and the average of the suspended dust \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Concentration** & **PSMA 6 mm** & **PSMA 8 mm** & **PSMA 10 mm** & **PSMA 13 mm** & **PSMA 19 mm** \\ \hline PM\({}_{0.3}\) & 2.43 & 1.41 & 1.82 & 1.32 & 1.35 \\ PM\({}_{0.5}\) & 3.52 & 1.35 & 1.98 & 1.70 & 2.76 \\ PM\({}_{1.0}\) & 2.70 & 1.61 & 1.61 & 2.29 & 2.48 \\ PM\({}_{2}\) & 3.07 & 2.48 & 2.81 & 3.62 & 4.25 \\ PM\({}_{5}\) & 0.46 & 0.47 & 0.58 & 0.61 & 0.94 \\ PM\({}_{10}\) & 0.77 & 0.86 & 0.99 & 1.08 & 1.97 \\ \hline TRWP & 2.0 & 2.2 & 2.4 & 2.5 & 3.3 \\ Emission (g) & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Suspended dust concentrations and TRWP emissions by maximum aggregate size. Figure 7: Results of cumulative number of wear particles over LTRWP test time. concentrations (\(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\)) recorded at 10 s intervals over 100 h was calculated. TRWP emission denotes the total amount of wear generated, and the weight (g) of the accumulated dust collected after completing the wear test was recorded for the TRWP emissions. According to the experimental results, the TRWP emissions collected after the completion of the test increased consistently as the NMAS of the PSMA mixture increased. A linear relationship equation showed the tendency of TRWP emissions to increase by approximately 0.15 g when the NMAS increased by 1 mm. Figure 8 presents certain specific test results. The TRWP emissions increased by 10%, 9%, 4%, and 32% when the NMASs increased from 6 mm to 8 mm, 8 mm to 10 mm, 10 mm to 13 mm, and 13 mm to 19 mm, respectively. In general, SMA mixtures with a maximum aggregate size of 13 mm are used. However, it was evaluated that the tire-pavement wear was reduced by 20% when the SMA mixture with a maximum aggregate size of 6 mm was used. It is determined that the wear reduction tendency based on the NMAS of the PSMA mixture evaluated in this experiment is attributed to the fact that the surface roughness of smaller aggregates increases the contact area of the tire compared to larger aggregates, thereby distributing the load and reducing wear. Figure 9 demonstrates the TSP test results for each NMAS of the PSMA mixture.