Long‐term post‐crack performance of high‐strength fiber‐reinforced concrete for structural applications

The post‐crack flexural‐tensile performance of fiber‐reinforced concrete (FRC) is a critical property of this material and is often the main justification for inclusion of fibers within a concrete mixture. Given the structural importance of this property, it is critical that performance demonstrated in pre‐qualification trials, and in quality control testing, is sustained throughout the design life of a structure reliant on post‐crack flexural‐tensile resistance. Previous research has indicated that an increase in compressive strength or paste hardness in maturing concrete can promote a change in fiber behavior at cracks from one of pull‐out to rupture. This can lead to a substantial fall in flexural‐tensile strength as the concrete ages. This behavior primarily affects low‐ to medium‐strength steel fibers in high‐strength concrete. It has been reported that use of very high tensile strength steel can preclude this transition, leading to sustained flexural‐tensile performance in late‐age high‐strength concrete. The current investigation has examined the evolution of flexural‐tensile behavior in high‐strength fiber‐reinforced concrete mixtures used in structural applications, to determine whether commercially available fibers made with high‐strength steel wire can resist rupture when the concrete compressive strength exceeds 80 MPa at over 5 years of age.