Effect of crimped synthetic fibre surface treatments on plastic shrinkage cracking of cement-based composites

Abstract

The plastic shrinkage and thermal shrinkage cracking of cement-based composites can be controlled by using fibre reinforcing, although the possible effects of fibre length or cross-sectional area or the hydrophilic and hydrophobic nature of the fibres used have not been evaluated comprehensively. In addition, there is some concern over the potential reduction of performance when fibre balling occurs, particularly with increased levels of added hydrophobic fibres. This study evaluated the effects of fibre length, diameter, volume fraction and hydrophilic treatment of crimped polypropylene fibres on controlling plastic shrinkage. The fibre surface was hydrophilised by applying maleic anhydride grafted polypropylene (mPP) granules. The crimped polypropylene fibres proved effective at controlling plastic shrinkage cracking of a cement-based composite, particularly when the fibre surface had been hydrophilised. Fibres with smaller diameters controlled cracking better, regardless of their length or proportion. For a given diameter at low fibre levels, the longer fibres performed best, although shorter fibres gave better results when the fibre amounts were high. Plastic shrinkage cracking control is enhanced significantly when the fibre surface is hydrophilised, regardless of fibre length or diameter.