Bond strength of tension lap splice specimens in UHPFRC

Outstanding tensile properties of ultra-high performance fibre reinforced concrete (UHPFRC) initiate innovative applications that take advantage of the bond improvement with reinforcement (precast element connections, seismic strengthening of deficient lap splices, etc.). Tests on lap splice specimens under direct tension were performed to investigate the influence of UHPFRC fibre content on bond strength. Three fibre contents (Vf) were examined with large reinforcing bar diameter (db) and multiple splice lengths. According to strain hardening response of UHPFRC under direct tension, results show a considerable improvement of bond performance and splitting crack control. For UHPFRC mix with Vf = 4% per volume, a splice length of 12 db was found sufficient to achieve yielding of 400 MPa reinforcement; with 10 db length a bond stress around 10 MPa is reached. The contribution of the fibres was clearly highlighted through this experimental study, a strong relationship between the bond performance and both the maximum tensile strength and strain ductility of UHPFRC was noted.