Crack development in steel fibre-reinforced concrete members with conventional rebars

Although concrete performance increased significantly during the last twenty years, durability of concrete structures still remain a major concern. In fact, while concrete permeability remarkably reduced, aggressive agents can still penetrate in the concrete structures through cracks which are generally present due to shrinkage or tensile stresses. A possible solution for crack control in structural members reinforced by conventional steel rebars is represented by Fibre Reinforced Concrete. In fact, fibre reinforcement improves the tension stiffening into the concrete portions between cracks and allows tensile stresses to be transmitted between the crack faces; both aspects reduce the crack distance and, as a consequence, the crack width. Within this framework, this paper aims to shed some new lights on the crack control exhibited by Steel Fibre Reinforced Concrete (SFRC), having high post-cracking residual strength, in combination with steel rebars. In this regard, 32 tension-ties under direct tension were tested. Special attention was devoted to the influence of SFRC post-cracking performance on crack formation and development. The results confirm the reduction in mean crack spacing (srm) with respect to the RC members. However, beyond nominal residual strengths around 5 MPa, no considerable reduction of the mean crack spacing is appreciated