Durability of FRP-to-concrete bonded joints subjected to accelerated ageing in laboratory and to field natural ageing

The longevity of Fiber Reinforced Polymer (FRP)-to-concrete bonded joints is vital for maintaining the structural integrity of various applications, particularly in infrastructure. This research focuses on understanding how both accelerated aging in controlled laboratory conditions and natural aging in real-world environments influence the performance of these bonded joints. In this investigation, double-lap shear specimens were exposed to accelerated aging protocols, involving combined environmental factors such as temperature variations and moisture exposure, over different aging cycles (100, 200, and 500). The laboratory tests aimed to mimic decades of exposure within a shortened timeframe, while field measurements provided insights into long-term in situ behavior. Accelerated aging tests were conducted in accordance with the NF T30–049 standard and included the use of strain gauges to monitor local deformation and stress distribution within the bonded joints. Key outcomes included average shear stress, failure loads, failure modes, and post-aging glass transition temperature. In parallel, natural aging was assessed through continuous monitoring of CFRP reinforcement on five bridges located in different environmental conditions, analysing failure modes, load-bearing capacity. Results from the accelerated aging tests identified a cycle threshold beyond which the durability of the bonded composite reinforcement can be considered validated. Conversely, findings from natural aging tests revealed no significant decline in the adhesion capacity of the CFRP reinforcements, reinforcing confidence in their durability. Overall, this study highlights the necessity of addressing both accelerated and natural aging assessments in the design and application of FRP-to-concrete strengthening systems. The findings contribute to the development of best practices for FRP applications in construction, ultimately enhancing the longevity and safety of reinforced concrete structures.