Pull-Out Behaviour of Hooked End Steel Fibres Embedded in Ultra-high Performance Mortar with Various W/B Ratios

Abstract

This paper presents the fibre-matrix interfacial properties of hooked end steel fibres embedded in ultra-high performance mortars with various water/binder (W/B) ratios. The principle objective was to improve bond behaviour in terms of bond strength by reducing the (W/B) ratio to a minimum. Results show that a decrease in W/B ratio has a significant effect on the bondslip behaviour of both types of 3D fibres, especially when the W/B ratio was reduced from 0.25 to 0.15. Furthermore, the optimization in maximizing pullout load and total pullout work is found to be more prominent for the 3D fibres with a larger diameter than for fibres with a smaller diameter. On the contrary, increasing the embedded length of the 3D fibres did not result in an improvement on the maximum pullout load, but increase in the total pullout work.Keywords: pullout behaviour, bond mechanisms, water/binder ratio, hook geometry, embedment length and fibre-matrix interface.

Steel fibers pull-out after exposure to high temperatures and its contribution to the residual mechanical behavior of high strength concrete

“…Pull-out tests made by Naaman and Najm [5] on different types of steel fibers (smooth, deformed and hooked end) embedded in mortar matrices with compressive strengths from 33 to 60 MPa indicate that deformed fibers resist pull-out in an oscillatory way, while hooked end fibers resistance decreases as the hook is straightened and travels along the matrix tunnel. As expected, pull-out load strength increases with the fiber embedded length but increments are more evident in straight fibers than in hooked end fibers [6,7]. Pull-out tests of fibers with an inclination of 30°s how an increase of strength with respect to aligned fibers but the pull-out strength decreases for inclinations greater than 45° [ 6,8].…”

Effect of inclination angle on hooked end steel fiber pullout behavior in ultra-high performance concrete

“…As a foundation to analyze the fiber effects on cementitious composite and the fiber-matrix bond relationship, fiber pullout test provides basic information and a comprehensive understanding on the bond-slip characteristics, and thus enables further improvement on the fiber-matrix interfacial properties [10,11]. The pullout behavior of a single steel fiber depends on many factors [12], including the fiber geometry, orientation angle, embedded length, matrix quality, as well as the pullout rate.…”

Active Reinforcing Fiber of Cementitious Materials Using Crimped NiTi SMA Fiber for Crack-Bridging and Pullout Resistance

“…Steel fibers are cheap and provide enough energy dissipation after cracking; they are commonly used with several shapes, such as end-hooked, twisted, and crimped [ 10 , 11 ]. These shapes help increase the mechanical bond resistance or end-anchoring resistance of steel fibers.…”