###### Abstract  
The application of reinforced concrete (RC) beam with near-surface mounted (NSM) pre-stressed carbon fiber reinforced polymer (CFRP) plates has been increasingly widespread in civil engineering. However, debonding failure occurs easily in the early loading stage because of the prestress change at the end of CFRP plate. Therefore, it is important to find reliable, convenient and economical technical means to closely monitor the secure bonding between CFRP and concrete. In this paper, an active sensing approach for generating and sensing stress wave by embedded smart aggregates (SAs) is proposed, which provides a guarantee for the secure connection between CFRP and concrete. Two specimens with different non-pre-stressed bond lengths were fabricated in the laboratory. Six SAs were installed at different positions of the structure to monitor the degree of debonding damage during the loading process. The experiments showed that the optimal length of non-pre-stressed CFRP bond section (300 mm) can significantly improve the load characteristics and enhance the service performance of the structure. The theoretical analysis of wavelet packet shows that increasing the length of non-pre-stressed CFRP bond section can slow down the occurrence and propagation of debonding cracks. The debonding crack in the tension end region is earlier than that in the bond end region. The research results reflect that the developed approach can monitor the damage process caused by debonding cracks and provide early warning for the initial damage and the debonding failure. carbon fiber reinforced polymer (CFRP); concrete; smart aggregates (SAs); active sensing approach; debonding detection +
Footnote †: journal: Appliedto improve the overall bonding performance between the CFRP and the concrete, giving full play to the strength of CFRP material. This structure is a new form of application that has many advantages over conventional reinforcement methods. The CFRP material can be easily embedded in the concrete structure to improve the deformation resistance since three sides of concrete groove participate in the bonding. The negative moment area is easy to reinforce and the strength of the CFRP material is fully utilized to effectively improve the ultimate bearing capacity of the structure. In addition, the NSM method prevents the destruction of CFRP materials by fire, and, furthermore, the NSM process reduces the workload of concrete surface treatment. Generally, CFRP strengthening technology includes external bonded method and NSM method [5]. Compared with the external bonded method, the advantages of NSM method have been proved [6]. The reinforcement technique of the NSM pre-stressed CFRP can solve the shortcomings of externally bonded CFRP and it is also proved to be one of the best reinforcement methods at present. But it is a difficult problem to find the best bond position of CFRP for reinforcement technology. At present, there are many studies on the debonding damage of CFRP-strengthened reinforced concrete structure but very few studies on RC structure with NSM pre-stressed CFRP plates have been reported. Therefore, this paper conducts an experimental research on the debonding damage of the RC beams with NSM pre-stressed CFRP plates. The optimal bonding position was found by using different CFRP bond section and health monitoring methods. However, the bearing capacity and safety of the structure are reduced due to overloaded vehicles, harsh environment, various corrosion [7], earthquake and aging of the structure. It is obvious that the demolition and reconstruction of these structures will cause great waste of resources, which is not suitable for the economic development of the country. Therefore, how to strengthen the structure reasonably has become a hot topic for experts and scholars in the civil engineering field. Moreover, it is an important subject in the field of civil engineering to use new materials to reconstruct and monitor the existing structure economically and reasonably.