Analytical Approach for Modelling the Pull-Out Mechanism of Recycled Synthetic Fibres in Fibre-Reinforced Concrete (FRC)

This study presents a simple one-dimensional analytical model describing the pull-out process of an elastic fibre embedded in a cement matrix, which captures the ductile behaviour of Fibre Reinforced Concrete (FRC) elements. The shear stress arising at the frictional interface between fibre and matrix during the pull-out is assumed to increase with the slippage distance, as a consequence of the growing abrasion of the fibre surface. The equilibrium conditions between the external axial load and the interfacial shear stress are imposed with reference to the undeformed configuration. The model is validated through comparison with both experimental data obtained by testing partially recycled polymeric fibres embedded in a cement matrix, and several datasets available in the literature comprising polypropylene fibres with and without silica coatings. The proposed model can properly describe the response of synthetic fibres that exhibit considerable axial elongation and slip-hardening interface behaviour. However, it may also predict the non-linear relation between the tensile load and the fibre displacement for different kinds of fibre, by setting adequately the constitutive parameters.