EXPERIMENTAL STUDY ON SPALL BEHAVIOR OF ULTRA-HIGH TOUGHNESS CEMENTITIOUS COMPOSITES

Spallation is a common failure mode of materials subjected to high-speed loads such as impact and explosion. The stress wave propagation and spall strength of UHTCC (Ultra High Toughness Cementitious Composites) has been studied experimentally using φ80 mm Hopkinson bar. Firstly, stress wave curves in UHTCC under strike pressures of 0.2 MPa, 0.3 MPa, 0.4 MPa and 0.5 MPa were measured through 5 strain gauges attached on specimen surface, and the spallation process of UHTCC were recorded by high-speed camera. Secondly, the stress wave velocity and dynamic elastic modulus in the material were calculated from the stress wave curves. Finally, the attenuation law of the stress wave propagation in the material was analyzed, and the spall strength and strain rate of the material under different strike pressures were calculated. The experimental results show that the spallation process of UHTCC exhibits more toughness characteristics than concrete; the peak value of stress wave in UHTCC decays rapidly in the range of 0 mm~500 mm; at the same strain rate, the spalling strength of UHTCC is about 10 MPa higher than that of concrete with similar static tensile strength, and the spalling strength of UHTCC has a significant rate effect.