Investigation of the Bond Behavior of the PBO Fiber-Reinforced Cementitious Matrix Composite-Concrete Interface

This paper presents the results of an experimental study conducted to understand the behavior and stress-transfer mechanism of fiber-reinforced cementitious matrix (FRCM) composites externally bonded to a concrete substrate for strengthening applications. The FRCM composite was comprised of a polyparaphenylene benzo bisoxazole (PBO) fiber net embedded within two layers of poly mer-modified cement-based mortar. Single-lap shear tests were conducted on specimens with composite strips bonded to concrete prisms. Parameters that varied were bonded length and width of composite. Additionally, the external coating layer of matrix was omitted on a limited number of specimens to examine the interfacial behavior between fibers and matrix and the role of the matrix in the stress transfer. Strain measurements along the composite bonded length were used to investigate the stress-transfer mechanism. Results suggest that the effective bond length of this composite is within the range of 250 to 330 mm (10 to 13 in.). Unlike with fiber-reinforced polymer (FRP) composites, no width effect was observed in terms of the maximum load. Finally, the stress-transfer mechanism at the matrix-fiber interfaces on either side of the fiber net was found to be unequal.