Concrete is the most widely used construction material as it offers low cost, general availability, and wide applicability. Concrete being a quasi-brittle material and it exhibits an increase in brittleness with increasing strength. Plain concrete has low tensile strength and toughness. Failure in concrete under applied tensile loading is associated with cracking. A crack is produced at low tensile stress and once formed it grows rapidly in the material. Concrete in the hardening state (after setting) develops tensile stress if volume changes due to shrinkage and thermal strains are restrained. Damage in tension develops at low tensile stress in the form of microcracks. The microcracks are formed even before the application of load. Under applied load, these micro-cracks coalesce to form visible cracks. Cracking leads to premature deterioration often resulting in a dramatic reduction in the service life and an increase in the life-cycle maintenance costs; cracks also accelerate deterioration by permitting the ingress of aggressive agents thereby producing corrosion of the steel reinforcement. Therefore improving the ability of concrete to carry tensile stresses is important to improve the service performance of structures
