Behavior of cementitious composites with randomly dispersed microfibers

Short carbon and steel fibers were used to reinforce high performance cement-based mortars. Effects of volume fraction, length and type of fiber as well as type of cement-based matrix were experimentally examined using uniaxial tensile specimens and three-point bend beams. The fracture properties were measured by a RILEM recommended test procedure. By incorporating the obtained matrix fracture properties, fiber aspect ratio and fiber-matrix interface bond into a fracture mechanical R-curve approach, mechanical responses of cement-based matrices reinforced by fibers can be predicted. Confocal microscopy was used to measure fracture surface roughness of the microfiber reinforced specimens. The roughness of specimens increased with increasing fiber volume fraction. Roughness was found to have a positive correlation with mechanical properties such as peak load in tension and flexure, K_IC and critical crack length.