Effects of steel fiber content and type on dynamic compressive mechanical properties of UHPCC

Abstract The split Hopkinson pressure bar (SHPB) test on Ultra-high performance cementitious composites (UHPCC) specimens is performed, in which the strain rate ranges from 17.6 s−1 to 328.4 s−1 and two typical steel fibers (micro-straight and hooked) with three volume fractions of 0%, 1.0% and 2.0% are considered. It indicates that, (i) the dynamic elastic modulus, compressive strength and peak strain as well as the toughness of UHPCC increase obviously with the increase of strain rate; (ii) the steel fiber content and type almost have no effects on the dynamic elastic modulus and peak strain, and show relatively small strengthening effects on the dynamic compressive strength of UHPCC; (iii) the present micro-straight steel fiber has slightly better effect on improving the dynamic compressive strength than the hooked steel fiber, particularly for the steel fiber volumetric ratio of 2.0%; (iv) the peak dynamic toughness almost has no relation to the steel fiber reinforcement, while the ultimate dynamic toughness increases with increasing the steel fiber content, and the influence of the micro-straight steel fiber is more obvious. Furthermore, the empirical dynamic increase factors (DIFs) for the dynamic compressive strength of UHPCC are formulated, and a modified visco-elastic damage model is established for UHPCC under dynamic loadings.