Properties of steel fibrous concrete containing mixed fibres in fresh and hardened state

The paper presents results of an experimental investigation carried out to study the properties of plain concrete and steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An experimental programme was planned in which various tests such as inverted cone time, Vebe time and compaction factor were conducted to investigate the properties of plain concrete and fibre reinforced concrete in the fresh state. Compressive strength, split tensile and static flexural strength tests were conducted to investigate the properties of concrete in the hardened state. The specimen incorporated three different volume fractions, i.e., 1.0%, 1.5% and 2.0% of corrugated steel fibres and each volume fraction incorporated mixed steel fibres of size 0.6 × 2.0 × 25 mm and 0.6 × 2.0 × 50 mm in different proportions by weight. Complete load deflection curves under static flexural loads were obtained and the flexural toughness indices were obtained by ASTM C-1018 as well as JCI method. A fibre combination of 65% 50 mm + 35% 25 mm long fibres can be adjudged as the most appropriate combination to be employed in SFRC for compressive strength, split tensile strength and flexural strength. However, better workability was obtained as the percentage of shorter fibres increased in the concrete mix.