Projectile impact resistance of fibre-reinforced geopolymer-based ultra-high performance concrete (G-UHPC)

This paper describes the mix design of geopolymer-based ultra-high performance concrete (G-UHPC) with the compressive strength from 100 to 150 MPa. Projectile impact tests at two striking velocities of-550 m/s and-800 m/s were then performed to explore the impact resistance of G-UHPC targets. G-UHPC without the addition of fibres yielded better impact resistance than Ordinary Portland Cement (OPC) concrete regarding crater damage and crack propagation, but inferior performance on reducing depth of penetration (DOP). The addition of fibres in G-UHPC effectively helped reduced DOP, crater damage and crack propagation. Steel fibres with a length of 10 mm and a volumetric fraction of 2% were most effective in resisting projectile impact compared with other G-UHPC specimens. To further comprehend the projectile impact performance of G-UHPC, a calibrated Karagozian and Case Concrete (KCC) model accounting for the strain rate effect was successfully used for G-UHPC in projectile analysis. Numerical results including single element and full-scale quasi-static tests, deceleration-time histories of projectiles during penetration and DOP of G-UHPC targets were obtained to validate the numerical models. After that, trendlines were regressed to predict DOP of G-UHPC at two striking velocities of-550 m/s and-800 m/s. Perforation limits of G-UHPC were also proposed for the design of both safe and costeffective protective structures against projectile impact, in which the perforation limits of G-UHPC were taken as 1.1 times of DOP. (c) 2021 Elsevier Ltd. All rights reserved.