## 1 Introduction  
In the construction industry, there is a growing shortage of high-quality natural aggregates [1; 2; 3; 4; 5]. To preserve the environment, substitute alternative concrete aggregates must be identified to promote more environmentally sound practices [6; 7; 8]. Recently, numerous studies have explored the use of blast furnace slag as a potential concrete aggregate [5; 6; 7]. slag, which is generated as a steel manufacturing by-product, crystallizes during the high-temperature discharge process, followed by cooling [9; 8]. slag is non-toxic to the environment because it is physically and chemically stable [5; 6]. Additionally, slag generated in the blast furnace has similar specific gravity to natural aggregates, making it highly suitable as an alternative to concrete aggregates [5; 6; 7; 8; 9; 10]. Research into the use of blast furnace slag as a concrete aggregate began in the 1980s [1; 2; 3]. In recent years, research efforts have focused on using waste slag (water-granulated quench blast furnace slag) as an admixture of cement and concrete [1; 2; 3]. In contrast, the use of air-cooled slag (ACS) has progressed more slowly, only recently being applied to non-structural concrete secondary products in which 90% of the ACS is recycled as a filler and landfill-type aggregate [10; 11; 12]. Therefore, it is necessary to study the application of continuous-use ACS aggregates to replace natural aggregates for improved environmental and economic efficiency [13; 14; 15; 16; 17; 18; 19; 20]. In a previous study that assessed the physical and mechanical properties of concrete, the air volume increased due to the pores in the aggregate, and the slump content decreased due to the increase in the absorption quantity of the mixing water [1; 16; 17; 18; 19; 20]. In addition, the increase in the number of pores reduced the concrete's strength and increased chloride ion penetration [1; 2; 21; 22; 23]. It is possible to fill the pores by applying fly ash (FA) and blast furnace slag (BFS) powder, effectively increasing the physical and mechanical properties of the concrete by increasing the fluidity via the ball-bearing phenomenon [1; 2; 21; 22; 23]. A rural road can be defined as a road that is directly used for the production activities of farmers in general connected to cultivated land. Therefore, it can be defined as a road on which agricultural machinery and the like mainly move, unlike general roads such as automobile-only roads. In a study on the physical and mechanical properties of rural-road pavement to which the existing ACS aggregate was applied, it was confirmed that an air-cooled slag aggregate has physical, mechanical, and environmental properties applicable to rural-road pavement [24]. However, the durability of concrete with ACS aggregate incorporation has yet to be evaluated. Compared with natural aggregates, the ACS aggregate has a large number of pores therein [24], which may affect the abrasion, freeze-thaw, and impact resistance of the concrete. Thus, in this study, we investigated the strength properties and durability performance of concrete containing an ACS aggregate in an attempt to optimize the concrete's durability. The purpose of this study was to evaluate the possibility of using the ACS aggregate as an aggregate for concrete through the durability evaluation of rural-road pavement concrete to which the industrial by-product, the ACS aggregate, is applied. To achieve this purpose, the target performance of rural-road pavement concrete was investigated. In addition, when there was no target performance standard, the performance was compared and evaluated with concrete that did not use the ACS aggregate. The target performance of the pavement concrete for rural roads with ACS aggregate application was \(\geq\)4.5 MPa flexural strength and \(\geq\)80% freeze-thaw resistance using the existing Agricultural Production Infrastructure Maintenance Business Plan's Design Criteria [25] and the Korea Expressway Corporation's Highway Specialized Specification [26].