# Laboratory Evaluation of Wear Particle Emissions and
## 3 Results
### Analysis of TRWPs for PSMA Mixtures
The average TSP of all test mixtures was measured to be 11 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\), the maximum TSP value for the 19 mm PSMA mixture was 13.7 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\), and the minimum TSP value for the 8 mm PSMA mixture was 8.2 \(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm{m}^{3}\). As the NMAS of the mixture increased, the TSP also tended to increase, similar to the results of the TRWP emission experiment. However, the TSP of the 6 mm PSMA mixture showed a higher value than the TSP measurements of mixtures with other aggregate sizes, contrary to the results of the TRWP emission experiment. Although the TSP generated in the 6 mm PSMA mixture is higher than the test results for other mixtures, the TRWP emissions were measured to be low. It can be interpreted that although it took a long time for the generated dust to be suspended in the atmosphere, the total amount of dust generated was low. Furthermore, it can be predicted that more small particles of \(\mathrm{PM}_{2}\) or smaller are generated from the 6 mm PSMA mixture than other mixtures. Similar to the hypothesis of this study, Figure 10 demonstrates that the 6 mm PSMA mixture exhibits a higher concentration of \(\mathrm{PM}_{2}\) or smaller suspended dust compared to the measurement values of other mixtures. In the test results of \(\mathrm{PM}_{5}\) or larger suspended dust, the 6 mm PSMA mixture exhibits a lower suspended dust concentration than that of other mixtures. Figure 8: Results of the TRWP emission tests on PSMA mixture with maximum aggregate sizes. However, the equipment used in this study does not support dehumidification while measuring suspended dust and weighing the collected dust. Hence, errors may occur in the measurement results due to humidity. In the case of suspended dust that is light and has small particle sizes (PM\({}_{2}\) or smaller), the suspended dust stays in the atmosphere for prolonged periods due to a vortex created by the tires, specimen rotating inside the tester, and the airflow flowing in from the cooler. Therefore, the concentration of newly generated suspended dust was measured, in addition to the concentration of the previously generated suspended dust still floating in the atmosphere, at each concentration measurement cycle (0.1 Hz). Hence, it is deemed that irregular measurement tendencies are caused by this phenomenon. In contrast, for suspended dust that is relatively heavy and has large particle sizes (PM\({}_{5}\) or larger), the time suspended dust stays in the atmosphere is reduced due to the sedimentation effect caused by gravity. Therefore, the cycle is stabilized in which newly generated wear particles from the friction between the mixture and the tires are suspended in the atmosphere, and previously suspended particles settle down to the bottom. Conse  
Figure 10: Results of suspended dust concentrations by PM size. Figure 9: Results of the TSP tests on PSMA mixture with maximum aggregate sizes. quently, the suspended dust concentration tends to increase according to the NMAX of the mixture. As shown in Figure 11, the concentrations of PM\({}_{5}\) and PM\({}_{10}\) suspended dust exhibited high coefficients of determination (0.9 or higher) in their relationship with NMAS. In the case of PM\({}_{5}\), the suspended dust concentration increased by approximately 0.04 \(\upmu\)g/m\({}^{3}\) when the NMAS of the mixture increased by 1 mm. For PM\({}_{10}\), the suspended dust concentration consistently increased by approximately 0.09 \(\upmu\)g/m\({}^{3}\) as the NMAS of the mixture increased by 1 mm.