Fracture Toughness of Microfiber Reinforced Cement Composites

An investigation into the reinforcing behavior of microdiameter fibers in cement composites, with an emphasis on their behavior in the frontal process zone (FPZ) ahead of the crack tip, is presented. Fracture toughness tests were conducted on thin sheet cement composites reinforced with polypropylene (PP), polyvinyl alcohol (PVA), and refined cellulose (RC) fibers under air-dry conditions. Fracture toughness in the absence of microscopic damage was quantified for these composites, as was fracture toughness that included the energy absorbed in the microcracked region prior to failure crack localization. These tests revealed that the PVA and RC fibers were able to effectively postpone microcrack formation, thereby delaying the localization of the failure crack. The PP fibers were not able to provide the same level of reinforcement. An optical microscope was used to monitor the progression of damage during testing. In addition, the acoustic emission technique was used to confirm the accuracy of the fracture toughness values.