## 4 Conclusions  
The purpose of this study was to replace natural aggregates, which are gradually being depleted as aggregates for concrete, with the ACS aggregate, which is an industrial by-product, and apply it to rural-road pavement concrete. To achieve this purpose, the performance of rural-road pavement concrete was evaluated through experiments when a natural aggregate was used instead of the ACS aggregate. The conclusions from the results of this study are as follows:  
1. As the amount of ACS aggregate increased, the flexural strength decreased. This result is because the ACS aggregate has many voids compared to the natural aggregate. However, the flexural strengths tested satisfied all target strength values (\(\geq\)4.5 MPa). The chloride ion penetration depth increased with the ACS aggregate's substitution ratio. In addition, when the GS and GG were used at the same time, the diffusion depth and  
Figure 9: Test results of repeated freezing and thawing cycles.  
diffusion coefficient decreased compared to the case where the GG was used. Therefore, it is effective to use the GG and GS at the same time.  
2. The durability test results of pavement concrete with the ACS aggregate showed that the ACS aggregate had no significant effect on the abrasion resistance of rural-road pavement concrete. The impact resistance decreased with the increased application of the ACS aggregate. The decrease in the resistance was larger when the GG was used relative to when the GS was used. As a result of the repeated wetting-drying test, the residual compressive strength slightly increased when the ACS aggregate was applied. In addition, the results indicated that the freezing and thawing resistance satisfied 80% of the relative dynamic elastic modulus targeted.  
3. Rural-road pavement shows an increase or decrease in durability items depending on the content of the ACS aggregate as a result of the durability test, but since the decrease is not large, it can be applied in terms of resource recycling.  
4. As a result of this study, the industrial by-product, the ACS aggregate, can be used in rural-road pavement concrete as an alternative to natural aggregates, so it has an excellent environmental effect in terms of resource recycling. However, in this study, the evaluation of cracks and microstructural characteristics in the concrete according to the application of the ACS aggregate was not conducted. Therefore, for future research, it is necessary to study the crack characteristics and microstructure analysis according to the use of the ACS aggregate. In addition, studies such as CO\({}_{2}\) emission analysis and economic feasibility analysis are needed in consideration of the environmental aspects of ACS aggregates.  
[PERSON] conceived and designed the experiments, [PERSON] performed the experiments and analyzed data, and [PERSON] analyzed data and wrote the manuscript. All authors have read and agreed to the published version of the manuscript.  
This study was carried out with the support of R&D Program for Forest Science Technology (Project No. 2021332B10-2123A01)' provided by Korea Forest Service(Korea Forestry Promotion Institute) and This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry (IPET) through Agricultural Foundation and Disaster Response Technology Development Program, funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA)(320047-05-2-HD020).  
Not applicable.  
The authors declare no conflict of interest.