Alignment of hooked-end fibres in matrices with similar rheological behaviour to cementitious composites through homogeneous magnetic fields

Abstract

The following study aim is to analyse the parameters affecting the alignment of hooked-end steel fibres (HSF) in fluid matrices with Yield Stress (), using homogeneous magnetic fields as a main source to modify their orientation. HSF are commonly used as reinforcement in composites in the construction industry, mainly in cementitious materials which also show . The parameters studied here are: on one hand those referring to the rheological properties of the matrix, mainly , and on the other hand those associated to the HSF: aspect ratio, geometry and magnetic dipole moment (). To do so, a homogenous Magnetic Field (MF) with controlled strength and time pulse was used to induce a torque to the HSF and hence to control their orientation by mean of turning fibres. The source to obtain the MF was designed to reach up to 10 mTeslas, using a Helmholtz coil of 10.5 cm radius.

The results obtained here assess how a MF with intensities adjusted to a known of a matrix can induce fibres orientation. Some steel fibre parameters such as geometry (specially length) and mass, affect considerably the total induced torque needed to rotate the fibres, and hence to align them in a matrix. Besides, rheological parameters can be also adjusted to achieve the fibre alignment, as well as the magnetic pulse shape and the magnetic field peak intensity.