Dynamic performance and structural evolution of corroded ultra-high performance concrete with initial defects under impact loading

This study addresses the dynamic performance and macro-micro structural evolution of corroded ultra-high performance fiber reinforced concrete (UHPFRC) with initial defects under high-speed impact loading. Integrated multi-scale experimental characterization (BSE, MIP, Nanoindentation and SHPB, etc.) and numerical simulation are employed to investigate the dynamic mechanical behavior and structural evolution of the damaged UHPFRC. Results show that initial defects induce micro-cracks and provide corrosion deterioration channels, leading to a more remarkable decrease in P-wave velocity and substantial loss of nano-mechanical strength in matrix and steel fiber. The MIP analysis reveals that the coupling effects of cracking and corrosion damage introduce a larger proportion of pores, the pore volume in the range of pore size larger than 100 nm rises, the dV/logD curves shift to high and gradually refine to multiple peaks. In terms of mechanical properties, coupling damages of initial defects and corrosion have a detrimental effect on the dynamic mechanical response. The HJC constitutive model in LS-DYNA is applied for the first time to describe the dynamic behavior of the various corroded UHPFRC containing initial defects, which is successfully validated to reliably predict the failure modes under different impact loading. The study benefits to better understanding prior to the design and application of impact-resistant UHPFRC.