Fibres and material comprising same

Synthetic fibre bundles for the prevention of the formation of self-induced cracks in a cement material comprising 10-10,000 filaments per bundle, the filaments consisting essentially of a polyolefin, a polyolefin derivative, a polyester or a mixture of the foregoing and having a length of 1 to 30 mm, a mean transverse dimension of 5 to 30 .mu.m and an aspect ratio of 100 to 1000, the filaments in each bundle being held together by a wetting agent, the wetting agent providing the individual filaments with a surface tension which allows them to become homogeneously dispersed in a concrete, mortar or paste with conventional mixing in conventional concrete mixing equipment.

A method for the prevention of the development of self-induced cracking in a cement material, the method comprising adding to a concrete, mortar or cement mix to which water has been added, an amount of 0.05 to 1% by weight, based on the cementitious materials, of synthetic fibre bundles comprising 10-10,000 filaments per bundle, the filaments consisting essentially of a polyolefin, a polyolefin derivative, a polyester or a mixture of the foregoing and having a length of 1 to 30 mm, a mean transverse dimension of 5 to 30 .mu.m and an aspect ratio of 100 to 1000, the filaments in each bundle being held together by a wetting agent, the wetting agent providing the individual filaments with a surface tension which allows them to become homogeneously dispersed in a concrete, mortar or paste with conventional mixing in conventional concrete mixing equipment.