Investigation of direct shear strength mechanisms of steel and PVA fiber-reinforced concrete

Some mechanical properties of concrete can be improved with the addition of other materials, such as the incorporation of fibers, which results in increased tensile strength and toughness, presenting post-cracking behavior that significantly contributes to the transfer of shear stresses, especially in planes that are propitious to the formation of cracks. To evaluate the effects of the addition of fibers to concrete, in terms of the ultimate shear strength and the mechanisms that constitute it, such as cohesion between the component materials, aggregate interlock, friction and dowel action, an experimental program was carried out. Two mixtures were produced from a conventional concrete mix, with the addition of 0.5% steel fibers and 0.2% synthetic polyvinyl alcohol, PVA fibers. Specimens for direct shear testing, push-off type, were molded, with and without transverse shear reinforcement, and a steel-concrete bond condition was set as a variable. The results showed that the addition of steel fibers results in a significant increase in the shear strength of concrete, na effect not observed with PVA fibers. The aggregate interlock and cohesion mechanisms were responsible for approximately 70% of the ultimate shear strength in all the concrete tested, while the rest was attributed to friction and the dowel effect.