Experimental investigation on static and dynamic mechanical properties of steel fiber reinforced ultra-high-strength concretes

Nowadays, high-rise, long-span and complicated structures are springing up. Accordingly, there is an increasing need for concretes with high strength even ultra-high strength, low cost and low construction difficulties. In the present study, steel fiber reinforced ultra-high-strength concrete (SFR-UHSC) was designed and produced with common materials and standard curing methods. To obtain a good performance, a low water-to-binder ratio of 0.22, a superplasticizer and several readily available mineral admixtures were applied. Static mechanical and Split Hopkinson press bar tests were carried out to evaluate the mechanical performances of SFR-UHSC. It is found that under static loadings, SFR-UHSC exhibits good ductility, toughness and plasticity. In details, compared with cubic and prism compressive strengths as well as Young's modulus of SFR-UHSC, much more increases of splitting tensile and flexural strengths are obtained by the introduction of steel fibers. When the volume fraction of steel fiber increases, the ratio between prism and cubic compressive strengths decreases while the ratio of tensile strength to compressive strength increases. On the other hand, in the scenario of high strain rate, SFR-UHSC has a good energy absorption capacity and compressive toughness. When subjected to impact loadings, SFR-UHSC cracks along various paths without fragmentation. Moreover, dynamic compressive strength is increased by both increasing strain rate and steel fiber content while its strain rate effect is slightly lower than that of ordinary concrete.