IMPACT COMPRESSION PROPERTIES OF NANO-SIO₂ MODIFIED ULTRA HIGH TOUGHNESS CEMENTITIOUS COMPOSITES USING A SPLIT HOPKINSON PRESSURE BAR

Ф80 mm Split Hopkinson Pressure Bar was used to study the dynamic compressive behavior of nano-SiO₂ modified UHTCC (Ultra High Toughness Cementitious Composite), and it was compared with that of steel fiber reinforced concrete and normal UHTCC. The quasi-static compressive strength and stress-strain curves under dynamic loads with 4 strain rates (2.36×10^-5 s^-1, 120 s^-1, 160 s^-1, 200 s^-1) were achieved in this experiment. Moreover, hybrid fiber effect of PVA and steel fiber on the impact resistant ability of materials was also studied in this research. The results showed that the peak compressive strength and specific energy absorption rose along with the increase of the strain rate for all groups. The dynamic stress and energy absorption ability of nano-SiO₂ modified UHTCC were higher than normal UHTCC. Besides, steel-PVA fibers had synergy on the dynamic behavior of UHTCC and it was improved with the steel fiber content increasing. However, the improvement of dynamic stress was dependent on synergistic relationship between the strain rate and the steel fiber addition.