Evaluation of hybrid fibre-reinforced concrete slabs in terms of punching shear

This study aims to investigate the influence of hybrid steel-polypropylene fibres in enhancing the capacity of punching shear with respect to concrete slab column connection. This paper adopted the experimental programme of studies to evaluate the influence of hybrid fibre on the punching shear as a key property of a concrete member. The experimental programme, supporting this investigation, involved samples of three mixtures in addition to a reference plain concrete mixture (PC). Fibre type and volume were the factors that have been used for determining these mixtures. The mixtures included single fibre concrete (SFC) mix with steel fibre volume of 0.5%, hybrid fibre-reinforced concrete mix (HFC1) with steel fibre volume of 0.5%, polypropylene fibre volume of 0.2%, hybrid fibre-reinforced concrete mix (HFC2) with steel fibre volume of 1.5%, and polypropylene fibre volume of 0.2%. The experimental programme adopted the use of 600 mm diameter circular slab specimens with overall depth of 75 mm to test the punching shear. The experimental study further investigated the influence of the hybrid fibres on other concrete properties including compressive and, flexural strength; 150-mm cubic specimens and 150 x 150 x 600 mm prismatic beams were used to measure the compressive and flexural strengths, respectively. The results of the study demonstrated a significant improvement in the punching shear capacity in hybrid fibre concrete mixes over plain and single fibre concrete mixes. This improvement has also been demonstrated in other concrete properties including compressive strength, flexural strength, cracking behaviour, ductility, and toughness. The improvement in the concrete properties was observed to be high in HFC2 mixture (0.2% PP, 1.5% SF), and on comparison with the plain concrete mixture a notable increase of 34% in punching sheer capacity was recorded. (C) 2020 Elsevier Ltd. All rights reserved.