## 1 Introduction  
In recent decades, the interest in developing effective repair and reinforcement methods to prolong the concrete structure service life has been increasing. Recent advancements in materials science have underscored the potential of composite materials, particularly carbon fiber-reinforced polymer (CFRP), for the reinforcement and repair of concrete structures [1; 2]. CFRP is especially valued for its high strength-to-weight ratio, corrosion resistance, and ease of application, making it an ideal candidate for structural enhancement [3]. Among the various techniques for reinforcing concrete structures with CFRP, the Near-Surface Mounted (NSM) method stands out [4]. This method involves embedding CFRP rods or strips into pre-cut grooves on the concrete surface and securing them with adhesives, typically epoxy resins. The effectiveness of the NSM method is highly dependent on the bond strength between the CFRP and the concrete, facilitated by the adhesive used. Extensive research has been conducted on the bond performance of CFRP systems using different types of adhesives. [PERSON] [3] discussed the implications of reinforcement corrosion on concrete integrity, emphasizing the need for durable repair solutions. [PERSON] et al. [5] and [PERSON] et al. [6] demonstrated the advantages of using CFRP for structural reinforcement, noting the NSM method's significant enhancement of concrete structures' mechanical performance. [PERSON] et al. [7] further elaborated on the challenges of preliminary debonding in bonded reinforcement systems and highlighted the NSM technique's potential to address these issues. The bond strength between the CFRP and concrete is crucial for the long-term performance and durability of repaired structures. Researchers have examined various parameters affecting this bond, such as the type of adhesive [8; 9; 10], curing conditions, and surface preparation of the CFRP and concrete [11; 12]. For instance, [PERSON] et al. [13], [PERSON] et al. [14], and [PERSON] et al. [15] explored the impact of different adhesives on bond strength, concluding that the adhesive's mechanical properties and its interaction with the concrete surface significantly influence the overall bond performance. The epoxy resin transfers shear stresses between concrete and the composite reinforcement [16]. This parameter affects the behavior and long-term durability of concrete structures undergoing repair through the NSM technique [17; 18]. Table 1 provides a general overview of recent studies related to the NSM technique.  
Based on the literature, all studies on the bond between CFRP and concrete using the Near-Surface Mounted (NSM) method have utilized either non-loaded epoxy resin or special cement as a sealing material between the concrete and reinforcement. These approaches inherently suffer from premature failure at the reinforcement-resin or resin-concrete interfaces. Additionally, while several studies have investigated the mechanical  
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and thermal properties of resins with mineral charges such as kaolin and sand glass powder, refs. [28; 29; 30; 31] none have explored the application of these loaded resins in the context of CFRP applications. This study addresses this gap by incorporating silica sand as a filler material in epoxy resin composites to enhance the frictional forces and improve the adhesion efficiency between CFRP and concrete in the NSM method. This innovative approach not only aims to mitigate premature failure issues, but also seeks to enhance the mechanical and thermal properties of the composite material, thus providing new perspectives for more efficient and durable applications in structural reinforcement. By exploring the use of silica sand-loaded epoxy resin in CFRP applications, this study opens new perspectives on improving the performance and reliability of structural reinforcement techniques. This innovative approach could pave the way for more efficient and durable solutions in the field of civil engineering.