Recent experimental investigations on reinforced UHPFRC for applications in earthquake engineering and retrofitting

The bond capacity and characteristic behaviour of steel rebars embedded in ultra-high performance fibre-reinforced concrete (UHPFRC) has been studied. Indeed, sufficient ductility is to be ensured by proper seismic-resistant detailing of reinforced (or fibre-only reinforced) UHPFRC structures. This research is especially important for UHPFRC mixes which, due to the high fibre content, are generally used without conventional passive reinforcement, such as stirrups and ties. Rebars provided with fibre optic sensors were used to precisely quantify the strain along the steel reinforcing bars and, hence, derive the bond stress-strain relationship between UHPFRC and bars. This also assists to determine the extent of the ductile microcracking phase. Pull-out testing was conducted on thin plates and thick blocks, both under quasi-static monotonous loading and repeated loading cycles. The results complement current understanding of the contribution provided by rebars to crack control in UHPFRC elements.