## 4 Conclusions  
This study was conducted to establish the utility of air-cooled slag aggregate, which is an underutilized byproduct of the steel industry, as an aggregate for concrete. The air-cooled slag manufacturing process was analyzed and adjusted to produce aggregates with appropriate physical properties. Rural-road pavement concrete containing these aggregates was then prepared and tested according to the design criteria of the Korea Ministry of Agriculture's Agricultural Production Infrastructure Maintenance Business Plan and the Korea Expressway Corporation's Highway Construction Specialized Specifications.  
As a result of evaluating the physical properties of the air-cooled slag aggregate produced as a concrete aggregate, the quality standards (KS F 2527) of the blast-furnace slag aggregate for concrete were satisfied.  
As a result of conducting a dissolution test in accordance with the Waste Management Act of the Ministry of Environment of the Republic of Korea and the Japanese standard JIS K 0058 to evaluate the environmental properties of the air-cooled slag aggregate, it was found that there was no effect on the dissolution of hazardous substances, as all the standards were satisfied.  
The slump and air-content values of the experimental mixtures met the targeted performance criteria. However, the slump decreased, and the air content increased, with increasing amount of air-cooled slag aggregate. This result was because the air-cooled slag aggregate had pores on the surface compared to the natural aggregate, which increased the absorption of mixed water and the contents of air.  
The compressive, flexural, and splitting tensile strengths of the experimental mixtures met the targeted performance criteria based on the design criteria of the Korea Ministry of Agriculture's Agricultural Production Infrastructure Maintenance Business Plan and the Korea Expressway Corporation's Highway Construction Specialized Specifications. However, as the content of the air-cooled slag aggregate increased, the strength decreased, and the coarse air-cooled slag aggregate had a greater effect on the strength reduction than the fine air-cooled slag aggregate.  
The chloride ion penetration of the experimental mixtures met the targeted performance criterion of the design criteria of the Korea Ministry of Agriculture's Agricultural Production Infrastructure Maintenance Business Plan and the Korea Expressway Corporation's Highway Construction Specialized Specifications. In addition, the amount of chlorine ion penetration increased as the content of the air-cooled slag aggregate increased.  
This study did not take into account the effects of different subsurfaces and subgrade conditions in rural areas. We assumed that the different subsurface and subgrade conditions do not affect the concrete pavement, and the performance was evaluated when air-cooled slag aggregate was used as the concrete pavement material.  
[PERSON] conceived and designed the experiments; [PERSON]-[PERSON] performed the experiments and analyzed data; [PERSON]-[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).