Permeability of cracked hybrid fiber-reinforced mortar under load

Crack development in concrete is known to be profoundly altered by the presence of fiber reinforcement. The use of reinforcing fibers is shown to produce a significant reduction in water permeability through a modification of crack topography. This has direct implications for improving durability because many deterioration mechanisms of cement-based materials require the ingress of water. An innovative test configuration has been developed to evaluate water permeability in mortar subjected to a uniaxial tensile load. This test, which does not produce a preferential path for crack development, is used to simultaneously investigate the effect of a hybrid blend of fibers on mechanical performance and permeability of cracked mortar. Two different size classifications of fiber, micro- and macrofiber, are combined to modify the cracking mechanisms during the pre- andpostpeak response, respectively. Specifically, the combination of steel and polyvinyl alcohol (PVA) microfibers (less than 12 mm in length and 22 ion in diameter) with a larger steel macrofiber in mortar significantly improved resistance to water permeation and displayed additive contributions to mechanical performance.