Fatigue performance of near-surface mounted CFRP strips embedded in concrete girders using cementitious adhesive made with graphene oxide

- NSM FRP strengthening of beams by cement-based adhesives under fatigue loading has not been studied.
- Cement-based adhesive (IHSSC-CA) is easier to use during NSM CFRP application than epoxy.
- Fatigue load range and frequency were designed to simulate service load conditions.
- Results show better composite action between NSM CFRP and concrete by using IHSSC-CA.
- A damage accumulation model of RC beams under fatigue loading is also proposed.

In this study, the flexural performance and effectiveness of the use of innovative high-strength self-compacting non-polymer cementitious adhesive (IHSSC-CA) for the strengthening and repair of reinforced concrete (RC) beams using the near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) technique under fatigue loading was investigated, with the purpose of improving the serviceability of these RC beams. Cementitious materials with graphene oxide were used to produce the IHSSC-CA. The effect of fatigue loading on the behaviour of all tested beams was assessed by monitoring the deflection, crack widths and strain in concrete, steel reinforcement and CFRP strips during fatigue loading. An analytical model is also proposed to predict the cumulative damage-fatigue life relationship. The test results show that using cement-based adhesive (IHSSC-CA) could represent an excellent alternative to epoxy adhesive, as it improves the serviceability of NSM CFRP-strengthened and repaired RC members. Moreover, the proposed damage accumulation-fatigue life model shows good agreement with the experimental results and can be used in the design of RC members strengthened and repaired with NSM CFRP using IHSSC-CA and epoxy adhesives.