Dynamic behaviors assessment of steel fibres in fresh Ultra-High Performance Concrete (UHPC): Experiments and numerical simulations

In this research, the dynamic behaviors of steel fibre in fresh Ultra-High Performance Concrete (UHPC) with different rheological characteristics are investigated. Except the experimental studies, the smoothed particle hydrodynamics (SPH) is employed to simulate the motion of steel fibres in UHPC slurry, while the effects of different boundary conditions and related mechanism are analyzed. The obtained results show that a new fibre settlement curve can be proposed and divided into three periods in UHPC cementitious paste, in which the buoyancy and resistance have been carefully clarified. Besides, it is observed that vibration conditions can significantly change the particle contact angle, while the shear-thinning/thickening could affect the apparent viscosity, both of which may disturb the settlement of steel fibres in UHPC. In general, this paper systematically reveals and summarizes a new law of fibre settlement in UHPC slurry, which is beneficial for a deeper understanding and controlling of steel fibre dynamic performance during casting process.