Effects of steel fiber content and type on static mechanical properties of UHPCC

Abstract A series of cubic/axial compressive, direct tensile, four-point and three-point flexural tests on Ultra-high performance cementitious composites (UHPCC) specimens are conducted, in which six volume fractions (0–2.5%) and two types (micro-straight and hooked) of steel fibers are considered. The full compressive and tensile stress-strain curves, the flexural load-deflection/CMOD (crack mouth opening displacement) curves are obtained. It indicates that, (i) the steel fiber content and type have obvious strengthening effects on the cubic compressive strength; (ii) for the axial compressive strength, the steel fiber type has little influence and the enhancing effect of the steel fiber content becomes less obvious when the volume fraction exceeds 1.0%; adding steel fibers has little effect on the compressive elastic modulus and Poisson’s ratio; (iii) for the direct tensile strength, the steel fiber content has remarkable effect; the present micro-straight steel fiber has relatively better effect than the hooked steel fiber under same mixing ratio; (iv) the steel fiber content and type almost have no effects on the first crack flexural strength and the corresponding deflection, but show considerable effects on the flexural strength, load carrying capacity, energy absorption capacity, fracture toughness and fracture energy.