Strain compatibility between HPFRCC and steel reinforcement

Abstract

To build reinforced concrete structures able to mitigate steel corrosion produced by environmental attack, a reduced crack width should appear in tensile concrete. At least in the serviceability stage, fibers added to ordinary concrete could be a way to satisfy this requirement. Depending on the type, on the volume content and on the aspect ratio of fibers, FRC (fiber reinforced concrete) can show a higher ductility and sometimes a higher tensile strength than ordinary concrete. However, with or without fibers, concrete cannot produce tensile strains totally compatible with those of the steel rebars. To overcome this problem, new FRCs, called High Performance Fiber-Reinforced Cementitious Composites (HPFRCC), have been recently tailored to develop an ultra-high ductility. In these composites, since the strain at maximum stress is higher than the steel strain at yielding, strain incompatibility vanishes. In the present paper, in order to prove the existence of compatible strains between steel and HPFRCC, numerical results and experimental measurements are compared. This is possible by introducing a mechanical model of tension-stiffening, and by referring to tests to reinforced HPFRCC elements in tension. The good agreement between theoretical and experimental results is also found for reinforced HPFRCC beams in bending.