Flexural strengthening of RC beams using UHPFRC laminates: Bonding techniques and rebar addition

Abstract

Ultra-high performance fiber-reinforced concrete (UHPFRC) is a cementitious composite with outstanding mechanical and durability properties. Accordingly, this study focuses on the behavior of reinforced concrete (RC) beams that were strengthened with UHPFRC laminates. Firstly, a preliminary study was carried out at material scale to evaluate the effect of fiber volume on the mechanical properties of UHPFRC, and to select suitable fiber reinforcement ratio for laminate production. In the second step, real-sized laminates were tested to define the bare properties of full-scaled laminate and observe the size effect according to material tests before applying them as a strengthening material. Thereafter, in the final step, flexurally deficient RC beams were strengthened with 30 mm thick UHPFRC laminates using two different bonding methods: gluing with epoxy and mechanical anchoring. In addition, longitudinal reinforcing bars were added into the laminates and their effectiveness was evaluated to improve the success of the applied methods. The results showed that UHPFRC laminate usage, especially in the case of anchorage, is an effective technique to improve the load carrying capacity of RC beams. Moreover, it was observed that adding reinforcing bars into the laminates could improve the efficiency of the applied method remarkably.