Abstract
This study is aimed at fully understanding the anchorage mechanisms of steel fibres with novel hook geometries, e.g. 4DH and 5DH fibres, which were subjected to pull-out loading. The fibres were also embedded in four different matrixes with a compressive strength ranging from 33 to 148 MPa. The results showed that the anchorage and pull out behaviour was not only dependent on the geometry of the hooked end of steel fibres, but also closely related to the characteristics of matrix. Both maximum pull-out load and total pull-out work of 5DH fibre were considerably higher than those of 4DH and the controlled 3DH fibres for all matrixes. All fibres embedded in normal strength concrete and medium strength concrete matrixes were completely pulled out without the occurrence of full deformation and straightening of the hook, while the controlled 3DH and 4DH fibres ruptured at hook portion when embedded in ultra-high performance mortar matrix. To fully utilize the high mechanical anchorage, 5DH fibres should be used for reinforcing high or ultra-high performance matrixes in practice.
Highlights
Nowadays one of the main challenging topics of concrete industry is how to improve the tensile response of cementitious materials in terms of strength and ductility
This paper experimentally investigates the pull-out behaviour of various hooked end fibres, dealing with varying parameters such as the geometry of end hooks, matrix compressive strength and fibre tensile strength, and quantify the effect of the hook geometry of 3DH, 4DH and 5DH fibres on pull-out response
It can be seen that the shape of the curves for 5DH fibres embedded in normal strength concrete (NSC) and medium strength concrete (MSC) matrixes behaves differently from the high strength concrete (HSC) and ultra-high performance mortar (UHPM) ones (Fig. 3)
Summary
Nowadays one of the main challenging topics of concrete industry is how to improve the tensile response of cementitious materials in terms of strength and ductility. The fibre contribution is mainly reflected when the concrete cracking initiates and often enhances the post-cracking behaviour due to the improved stress transfer provided by the fibre bridging of the cracked sections [5, 6]. Bond is the mechanism through which tensile forces are transmitted between the steel fibres and the surrounding cement paste [8]. A part of these forces are resisted by the cementitious matrix, whilst the remainder is resisted by the fibres [9]. The tensile strength of steel fibre-reinforced cementitious composites (SFRCCs) can be quite variable, depending mainly on the fibrematrix bond strength [10, 11]. In case where the fibres have a weak bond with the matrix, the pull-out at low
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