## 1 Introduction  
Concrete recycling can be implemented as a strategy to reduce carbon emissions and promote sustainable development [1; 2; 3]. Concrete with recycled aggregates is recognized as one of the most prominent eco-friendly concretes [4; 5; 6]. Another concern for using recycled aggregates is that the supply of quality natural aggregates is diminishing in certain regions of the world (e.g., [7]). Of particular concern is increasing amounts of construction and demolition waste [1; 8; 9], from which recycled concrete aggregates (RCA) are derived. Consequently, concrete recycling and sustainable development are considered highly important in the construction industry [1; 10; 11]. Recycled concrete can be utilized by crushing discarded concrete debris and using it as RCA to partially or fully replace natural aggregates in new concrete [1]. Recycled aggregates can be classified depending on the particle size or the type of waste material [12]. Among them, coarse recycled aggregates produced from crushed concrete are the most used in concrete production, and they are referred to as recycled concrete aggregate or RCA [12; 13; 14; 15; 16; 17; 18]. The surface of RCA can consist of natural aggregate and adhered mortar, which results in RCA having different physicochemical properties compared to natural aggregates [19; 20; 21; 22; 23; 24]. The adhered mortar is porous, resulting in higher water absorption capacity in RCA compared to natural aggregates [19; 25]. Additionally, the roughness of the adhered mortar increases the surface area of recycled aggregate particles, requiring more water for achieving consistent workability compared to concrete made with the same natural aggregates [19]. As a result, the mechanical properties of concrete with RCA can be inferior to those of concrete using natural aggregate particles [19; 20; 21; 22; 23; 24]. Therefore, a number of researchers have explored methodologies to limit the detrimental effect of RCA, such as through beneficiation methodologies (e.g., [26; 27]), mix design approaches (e.g., [28; 29]), or alternative mixing approaches (e.g., [13; 30; 31; 32]). A significant number of researchers have noted that the moisture content of the RCA at the time of concrete batching can have a significant impact on the properties and performance of the concrete (e.g., [33; 32]) in addition to affecting the microstructure development [33; 34; 35]. [PERSON] et al. [36] discussed concrete compressive strengths with three different RCA moisture conditions--air dry (AD), oven dry (OD), and saturated surface dry (SSD)--and argued that SSD aggregate would release water, resulting in a weakened interfacial transition zone (ITZ) and a higher water-to-cement ratio [12]. These AD, OD, and SSD moisture states represent different moisture levels in RCA and play a crucial role in concrete performance. AD refers to aggregates dried naturally under atmospheric conditions, while OD indicates aggregates dried in an oven to remove all moisture. SSD signifies aggregates with their surfaces saturated with moisture but not immersed in water. [PERSON] et al. [32; 33] found that partially saturated RCA has the potential to have an equivalent concrete strength compared to natural aggregate concrete, and [PERSON] et al. [23] recommended to use partial SSD rather than SSD to secure the compressive strength of concrete with RCA. [PERSON] et al. [37] argued that recycled aggregates within an SSD condition have the most negative impact on concrete strength, while AD recycled aggregates optimize concrete strength [37]. The objective of this study is to explore the relationship between the compressive strength of concrete and the moisture content of recycled concrete aggregates (RCA) through the application of machine learning, since there are conflicting conclusions in the literature.