A quantitative study on the plastic shrinkage cracking in high strength hybrid fibre reinforced concrete

High strength concrete using silica fume is prone to plastic shrinkage cracking in dry and windy conditions. Addition of fibres is known to restrict the growth of shrinkage cracks. The present study was aimed at controlling plastic shrinkage cracks in high strength silica fume concrete by means of adding fibre reinforcement up to 0.5% by volume of concrete. Individual steel fibres as well as hybrid combinations of steel and non-metallic (polyester, polypropylene and glass) fibres were evaluated for their influence on plastic shrinkage cracking. Results showed that hybrid fibres were most effective in reducing shrinkage cracks. Among the hybrid fibre combinations, the steel and polyester combination was found to reduce plastic shrinkage cracks by more than 99% compared to the plain concrete. Increased fibre availability and low stress levels at early ages were the main factors contributing to the good performance of hybrid fibre mixtures.