Blast response of retrofitted reinforced concrete hollow core slabs under a close distance explosion

•Externally bonded reinforcement (EBR) are an efficient technique to upgrade the blast resistance of the hollow core slabs.•Under a close distance explosion, the propagation of the blast wave through the concrete cause a longitudinal crack in the critical zone where the ribs of the hollow cores have the smallest thickness.•The longitudinal crack extending into a vertical crack trigger local initiation of debonding between the carbon fiber reinforced polymer (CFRP) and the concrete.