Tensile behaviour and full-field strain of reactive powder concrete under dynamic loading: Effects of fibre length and content

The effects of steel fibre length and content on the dynamic splitting tensile properties of reactive powder concrete (RPC) were investigated using a Split Hopkinson Pressure Bar (SHPB). Because of the transient nature of dynamic loading, measurement of dynamic tensile strain and establishment of stress-strain relationship in dynamic splitting tests were challenging. In this study, the surface deformation and propagation of cracks in specimen during dynamic failure was recorded by high speed camera and analyzed by digital image correlation (DIC). The dynamic splitting stress and energy dissipation of RPC were determined with the tested stress waves in SHPB, and the time axis of full field strain and stress were synchronized using the stress synchronization system. The results show that, different from the static condition, the effects of steel fibre length and content on enhancing the strength are insignificant under dynamic loading. DIC analysis showed that the crack width propagation of RPC was similar under dynamic loading, regardless of fibre length and content. At the stress decrease stage, the splitting stress at a specified crack width is highest for the sample reinforced with long steel fibre and lowest for the sample without steel fibre, indicating that longer fibres have better bridging effect which makes the stress-strain curve flatter at the stress decrease stage. The effects of steel fibre on enhancing the dynamic energy dissipation are significant. With the increase of strain rate, the fibre length shows more significant effects on the dynamic energy dissipation, compared with fibre content.