Understanding the effects of hooked-end steel fibre geometry on the uniaxial tensile behaviour of self-compacting concrete

Abstract

A series of uniaxial tensile tests on cylinders made from steel fibre reinforced selfcompacting concrete (SFR-SCC) have been carried out to investigate the influence of fibre geometry and the combined effect of fibre content and distribution on the post-cracking behaviour. Three types of commercially available hooked end fibres (3D (single hooked), 4D double (double hooked) and 5D (triple hooked)) have been used in this study, which are added to the concrete mixture at two fibre dosages (0.5 and 1% by volume). The experiments show that the post-cracking strength increases significantly (P˂ 0.05) with the increase of fibre content for all mixtures. The combination of a unique shaped hook of high tensile strength demonstrates an optimum effect on the failure mode of concrete cylinders in which peak and post-peak strengths are raised. Notably, strain-hardening behaviour is observed only for cylinders reinforced with 5D hooked end fibres. A correlation between number of fibres exposed on fractured surfaces and post-cracking behaviour is established.

Study of three distinct self-compacting concretes containing marble/granite powder and hooked-end steel fiber contents

“…3 D, 4 D and 5 D) designated as Dramix V R has been widely reported. [29][30][31] Ghasemi et al 29 have reported the effects of distinct steel fiber proportions in a SCC (i.e. 0.1, 0.3 and 0.5% corresponding with 7.8, 23.5, and 39 kg/m 3 ).…”

Effects of Hooked-End Steel Fiber Geometry and Volume Fraction on the Flexural Behavior of Concrete Pedestrian Decks

“…Given the same fiber volume fraction, the 5D hooked-end fibers have the best flexural performance including the load-carrying capacity and post-peak ductility, followed by the 4D and 3D hooked-end fibers, respectively. This is mainly caused by their better pullout resistance, i.e., higher bond strength and pullout work, as reported by some previous studies [10][11][12]. The higher number of hook ends requires a higher force to bend more plastic hinges; hence, the 5D hooked-end fiber had the highest pullout resistance, followed by the 4D and 3D fiber, based on an assumption that the cement matrix was strong enough.…”

“…Such a superior bond performance is achieved because of the improved mechanical anchorage, owing to the increased number of hook ends. The peak and post-peak tensile strengths of steel fiber-reinforced concrete (SFRC) with conventional 3D hooked-end fibers were significantly enhanced by using the 4D and 5D hooked-end fibers, according to a previous study performed by Abdallah et al [11]. The 5D hooked-end fiber specimen only exhibited a re-increase in tensile stress (hardening) after a sudden drop in the stress by matrix cracking because of its stronger pullout resistance than the others (i.e., 3D and 4D hooked-end fibers).…”

“…The higher number of hook ends requires a higher force to bend more plastic hinges; hence, the 5D hooked-end fiber had the highest pullout resistance, followed by the 4D and 3D fiber, based on an assumption that the cement matrix was strong enough. Abdallah et al [11] reported that the tensile strength and post-cracking hardening behavior of concrete are enhanced by adding 0.5% and 1% hooked-end steel fibers and the 5D hooked-end fiber results in the best tensile performance. Given the identical fiber volume fractions of 0.5% and 1%, only the specimens with 5D hooked-end fibers exhibited a re-increase in the tensile stress after cracking, called hardening, while the others with 3D and 4D hooked-end fibers did not show the hardening behavior.…”

“…In recent years, some researchers [10][11][12][13][14] developed a novel multiple hook-end steel fiber and verified its effectiveness based on pullout and tensile tests. Abdallah and Fan [10] reported that the maximum pullout load and energy of conventional hooked-end steel fibers with three-dimensional (3D) geometry are significantly improved by using four-dimensional (4D) and five-dimensional (5D) geometries.…”