## 4 Conclusions  
This study was conducted as part of a basic research study executed to reduce scattered PM generated from road excavation-restoration work. The PM\({}_{10}\) emission trend for each excavation-restoration work activity was identified and the PM emission characteristics were analyzed according to the PM microstructure and cutting depth during asphalt concrete cutting activities. The major findings of this study are outlined below.  
As a result of measuring the PMC of scattered PM\({}_{10}\) in the road excavation-restoration work, it was found that large quantities of PM were generated immediately after the cutting blade of the cutter touched the surface, when the ground was vibrated by the breaker, when the excavator scraped the road surface, when the excavated soil was loaded onto a dump truck, and when the asphalt was poured and compacted. Furthermore, the road-cutting activity showed a tendency to emit the largest PM\({}_{10}\) quantities.  
The asphalt concrete specimen cutting-activity was performed in a small, enclosed chamber. During the cutting activity, the PNC and PMC of PM\({}_{10}\) rapidly increased immediately after the cutting blade touched the cutting surface. As a result of the analysis of scattered PM, the PMC of scattered PM\({}_{10}\) generated from the cutting activity tended to decrease as the cutting depth increased. Moreover, the number of particles exhibited the same trend.  
The analyzed results of the deposited PM showed that the deposited PM increased as a function of the cutting depth. In the case of wet cutting, the PMC of scattered PM\({}_{10}\) decreased by approximately 90.7% compared with dry cutting, but the deposited PM increased by approximately 37%. The ratios of PM collected on the filter compared with the deposited PM were 10.25%, 4.90%, 3.54%, and 0.20%. Thus, the ratios of scattered PM decreased as the cutting depth increased. This finding is related to the analyzed results of scattered PM. The deeper the cutting depth is, the larger the space inside the cut surface and in the voids in the asphalt specimen wherein PM can reside. As a result, scattered PM decreased and deposited PM increased.  
As a result of the SEM and EDS analyses, three types of PM were found to be generated from the asphalt concrete specimen-cutting activities. Type-1 PM are considered to be carbon compounds, and are mainly composed of asphalt binder. Type-2 PM are considered to be quartz particles from the aggregate part of the asphalt concrete specimen. Type-3 PM, unlike the above two types, are composed of C, O, Al, Si, and Mg, and Na, S, and K were also detected in various quantities. They can be composed of Al-Si-O, Ca-Al-Si-O, Fe-Al-Si-O, K-Al-Si-O, and Ti-Al-Si-O, and may also contain other similar compounds. Thus, they are considered to be naturally occurring aluminosilicate minerals.  
The XRD analysis results of the PM generated from the asphalt concrete specimen-cutting activity showed that the main components of the aggregate were detected rather than the components of the asphalt binder. This suggests a trend similar to those observed in the SEM and EDS analysis outcomes.  
Data curation, S.H. and J.L.; Writing--original draft, S.H. and J.L.; Writing--review & editing, C.B.; Supervision, C.B. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure, and Transport (Grant No. 22 POQW-B152342-01).  
**Institutional Review Board Statement:** Not applicable.