Carbon Fiber-Reinforced Polymer Rod Embedment Depth Influence on Concrete Strengthening

The use of carbon fiber-reinforced polymer (CFRP) rods offers a good solution for external strengthening of flexural reinforced concrete (RC) members. Limited data are available on the behavior of beams externally reinforced with CFRP rods under a loading–unloading protocol, which is of great importance for structural components subjected to vehicle loading. The embedment depth mandated by the majority of standards cannot always be acquired due to concrete cover limitations; the influence of embedment depth under this loading–unloading sequence needs to be investigated. This research studied the effects of rod embedment depth by comparing fully-embedded rods with half-embedded rods under a loading–unloading protocol and comparing the results with monotonic responses. An identical specimen without CFRP reinforcement functioned as the controlling element. The near-surface mounted technique (NSM) was used to integrate the rods with the concrete. The results show that CFRP rods positively affect the load-carrying capacity under a loading–unloading condition. The rods reduce the member’s ductility under monotonic loading but have no negative impact under loading–unloading. Whereas the difference in embedment depth configuration slightly affected the enhancement under monotonic loading, the half-embedded rods drastically reduced the capacity improvement under the loading–unloading sequence. An embedment depth deviating from the advised depth, should not be implemented for members subjected to a loading–unloading condition. The CFRP placement method had an impact on the failure behavior of the elements. The half-embedded rod failed by debonding between the rod and the epoxy resin, while the fully-embedded members were characterized by concrete spalling.