MULTIPLE IMPACT COMPRESSIVE PROPERTIES AND CONSTITUTIVE MODEL OF ULTRA-HIGH TOUGHNESS CEMENTITIOUS COMPOSITES

The mechanical properties of ultra-high toughness cementitious composites (UHTCC) under multiple impacts were studied using an 80-mm split Hopkinson pressure bar (SHPB). The evolution law of the stress-strain curve under different numbers of impacts was analyzed and compared with that of other fiber reinforced concrete. The experimental results show that under multiple impact loads, the strain rate increased exponentially with the increase of the number of impacts due to damage accumulation. The peak strength of UHTCC decreased linearly with the strain rate, while the peak strain and cumulative energy absorption increased gradually. The single energy absorption value increased first and then decreased with the increase of the number of impacts. The thermal activated damage evolution (TADE) model could only describe the mechanical response of UHTCC upon the first impact, but could not reflect the evolution law of the mechanical properties under multiple impacts. Comparatively, the damage evolution model based on Weibull distribution could well reflect the cumulative damage evolution law and the stress-strain curves of UHTCC under multiple impacts. According to the calculation of the damage degree, the sample could be considered to have been completely damaged after the third impact. However, the sample could still be kept as a whole by the bridging effect of the PVA fibers. It demonstrated its good crushing resistance capacity.