Anchorage mechanisms of novel geometrical hooked-end steel fibres

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 pullout 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.