Extruded Fiber-Reinforced Composite

Abstract

High performance fiber-reinforced cementitious composites (HPFRCC) exhibit increased tensile strength, enhanced toughness, and sometimes, a strain-hardening response. The amount of fiber reinforcement needed to achieve this behavior is higher than what can typically be added to conventional cast-in-place concrete. This chapter presents the mechanical properties of extruded HPFRCC containing several fiber types, along and in hybrid combinations. Hybrid composites containing two or more fiber types can be considered to optimize the desired properties of composites by taking advantage of the properties of each fiber. Polypropylene fibers have a lower elastic modulus than the cementitious matrix and a relatively poor fiber-matrix bond, while glass fibers have a higher elastic modulus than the cementitious matrix and a relatively strong fiber-matrix bond. Fly ash can replace cement in extruded composites. Its round particle morphology serves as a rheological aid. It is less expensive and more environmentally sound than cement. Fly ash also improves the mechanical performance of extruded composites, especially those containing glass fibers. The replacement of 70% of the cement, by volume, with fly ash in a glass-fiber extruded composite increases the strength by 10% and the toughness by 50%. This improvement in performance might be a result of an increase in porosity with the addition of fly ash, which weakens the bond strength enough to increase fiber pullout at failure.