Durability enhancements of cracked concrete by fibers

Synopsis: Permeability and cracking affect the durability and integrity of a structure. The addition of reinforcing fibers changes the cracking process in cement based composites. The goal of this paper was to review the research work related to the effect of fiber reinforcement on tensile cracks and water permeability of cementitious composites. Factors affecting this relationship included matrix type, fiber type, geometry and volume fraction, and crack width. Water flow was studied through individual fiber and hybrid fiber reinforced composites. Width-controlled tensile cracks were induced for the polyvinyl alcohol (PVA) and steel fiber reinforced composite samples by feedback-controlled split tension or by feedback controlled wedge splitting. Then water flow was measured with a low pressure test set up. For the hybrid fiber reinforced composites containing blends of macro- steel and microsteel and PVA fibers tensile cracks were induced by uniaxial tension, while water was forced through the samples under a relatively low pressure. The addition of fibers had beneficial effects on water flow for cracks in the micron range. This was mainly due to changes in crack morphology compared to unreinforced composites and multiple crack development. Permeability thresholds were identified for the crack widths, which varied with the matrix type and the fiber type. Synergistic effects of micro- and macrofibers were obtained through engineered composites mix designs, and hybrid fiber reinforcement showed improved results in terms of mechanical performance and permeability of cracked cementitious composites compared to single fiber reinforcement.