INTERFACE PROPERTY AND APPARENT STRENGTH OF HIGH-STRENGTH HYDROPHILICFIBER IN CEMENT MATRIX

This study addresses the characterization of fiber-matrix interfacial properties and the apparent strength of high-strength hydrophilic fibe rs. Single-fiber pullout bond tests and single-fiber pull-to-rupture s trength tests were conducted by employing polyvinyl alcohol (PVA) fibe rs. The pullout bond tests showed that these fibers have surprisingly high chemical and frictional bond strengths. The chemical bond strengt h was relatively stable independent of a water-to-cement ratio of matr ix and the fiber type tested, contrary to the friction bond strength. The pull-to-rupture strength tests revealed that the apparent strength of the PVA fibers in cementitious composites is considerably lower th an that in standard fiber strength tests. The apparent strength was fu rther reduced with inclining angle of fiber alignment. This effect was captured by a simple phenomenological model in this study, which intr oduces the apparent strength reduction factor. The combined effects of high bond strength and degraded fiber strength will likely contribute to composite performance less than would be expected from a high-perf ormance fiber.