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

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 (V f ) of 0, 0.5, 1.0 and 1.5%, the concrete compressive strength was 35 MPa and the maximum coarse aggregate size (D max ) 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 V f = 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 D max = 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 V f = 1.5% with the maximum coarse aggregate particle size of 25 mm and variability between the proposed analytical models of 2–7%.