Measuring and Modifying Interface Properties of PVA Fibers in ECC Matrix

Abstract

A single fiber pullout test was used in this study to measure the bond properties of polyvinyl alcohol fibers that are available at various diameters in a mortar matrix. Despite short fiber embedment lengths, the small diameter fibers ruptured during the pullout tests. However, it is shown that even if full fiber pullout is not achieved, it is still possible to determine a chemical debonding energy, G d , and an initial interfacial frictional bond strength, 0. Despite high G d values, the fibers did not rupture during the fiber chemical debonding process, but during fiber pull-out, a strong slip-hardening effect, characterized by the high values of the sliphardening coefficient, ␤, induced severe abrasion damage visible under scanning electron microscope on the fiber surface. As a consequence, when the fiber apparent tensile strength was exceeded, fibers ruptured by delamination. Finally, an attempt was made to lower the values of the bond properties to minimize fiber rupture during pullout. This goal was partially achieved by applying an oil coating on the hydrophilic polyvinyl alcohol fiber surface to reduce any strong fiber/mortar interaction.

Fiber-Bridging Constitutive Law of Engineered Cementitious Composites

“…The scenario; however, may be different in PVA fiber system, where strong slip-hardening behavior is present. Redon and Li (2001) suggested that sliphardening of PVA fiber in a cement matrix was due to an abrasion and jamming effect during sliding of the fiber in the matrix tunnel. Figure 4 shows typical responses of single PVA fiber pulled out from ECC mix 45 (M45) matrix.…”

“…The magnitude of the drop can be used to calibrate the chemical bond G d . During the debonding and pullout stages, the fiber may rupture if the load P exceeds the fiber tensile strength, which is often the case in PVA-ECC system due to strong slip-hardening effect (Redon et al 2001).…”

“…Among them, all fiber parameters E f , L f , and d f are measurable with good accuracy. The apparent fiber strength σ fu and fiber strength reduction coefficient f' were measured by single fiber in-situ strength test (Kanda and Li 1998) and interface properties τ 0 , G d , and β were measured by single fiber pullout test (Redon et al 2001). To measure the interfacial bond properties of ECC with different fiber volume content, M45 mortar matrix with the presence of 0.1, 0.5, and 2 vol.% PVA fibers were cast into molds and single PVA fiber was surrounded by the ECC matrix.…”

Comportamiento mecánico de hormigones de escoria activada alcalinamente reforzados con fibras de acero

“…Estas grietas pueden estar localizadas en los bordes entre la fibra y la matriz endurecida, favoreciendo que la fibra se desprenda mientras se transfiere la carga a la grieta principal. Este proceso es deseable, ya que el compuesto exhibirá un comportamiento de endurecimiento por deslizamiento, debido al fisuramiento múltiple de la matriz reforzada (33). Complementariamente, el C-S-H tipo gel generado en sistemas de activación alcalina presenta una alta densidad, lo que permite que éste pueda actuar como taponador de poros, y que dé lugar a un efecto de cicatrización que previene la propagación de la falla (34).…”

Interface Characterization of Different Types of Fibers in Engineered Cementitious Composites (ECC)

“…In 2001, Redon, Li, Wu, Hoshiro, Saito and Ogawa [20] used a single fiber pullout test to measure the bond properties of polyvinyl alcohol fibers that are available at various diameters in a mortar matrix. Despite short fiber embedment lengths, the small diameter fibers ruptured during the pullout tests.…”