Proposal for characterisation of direct shear strength of steel-fibre-reinforced concrete

Abstract

A proposal for the direct pure shear characterisation of steel-fibre-reinforced concrete specimens with two grooved shear planes is presented. In the first stage of work, crimped steel fibres (CSF) were used at volume fractions (Vf) of 0, 0.5, 1.0 and 1.5%, the concrete compressive strength was 35 MPa and the maximum coarse aggregate size (Dmax) was 9.5 mm. With these specifications, eight block specimens were subjected to the direct shear tests. A significant gain in shear strength was observed with an increase in fibre dosage – an increase of 90% when Vf = 1.5%. Based on this, three analytical expressions to compute the shear stress were formulated. The models were assessed by testing 15 blocks of smaller size and additional variables – hooked-end steel fibres (HSF), concrete compressive strength of 25 MPa and coarse aggregates with Dmax = 9.5, 19.0 and 25.0 mm. Better performance was obtained with the CSF rather than the HSF, with a strength gain of around 100% for Vf = 1.5% with the maximum coarse aggregate particle size of 25 mm and variability between the proposed analytical models of 2–7%.