Shrinkage of Steel-Fibre-Reinforced Lightweight Concrete

Abstract

Long-term behaviour of steel fibre reinforced concrete remains rather unknown and to a large extent unquantified by equations and standards. This paper studies experimentally the free drying shrinkage of steel fibre reinforced lightweight concrete during the first 28 days using 100 × 100 × 500 mm beams. The coarse lightweight material tested (LYTAG) is recycled and offers an alternative to gravel and quarry resources which are subjected to depletion in the future. Also, this material can lead to reduction in the mass of the structure which results in economical designs. However, LYTAG aggregate can absorb up to 15% of its own weight in water. This makes it susceptible to drying shrinkage both at young age and long-term due to environmental diffusion. Shrinkage can have a detrimental effect on the concrete by inducing cracks, creating therefore weak zones in the concrete. It is thought that fibres can have a favourable effect on the reduction of shrinkage due to their ability to bridge cracks. This could be vital particularly in large concrete flat slabs, joints, beams and even columns. This project uses modern hooked-end DRAMIX 3D and 5D fibres with different dosages Vf and number of hooks and evaluates shrinkage for concrete with different characteristic strengths fck.