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The flexural and tensile strengths, the shrinkage characteristics of concrete, the load-transfer capabilities at a crack and structural performance of the slab are significantly enhanced by the introduction of steel fibres into the concrete mix. Fibres of materials other than steel are used to reduce plastic shrinkage, i.e. shrinkage in wet concrete under unfavorable environmental conditions.

 

The fibre content should be at least 40 kg/m3. However, amounts in excess of 100 kg/m3 impair the workability of the concrete.

The influence of fibre length on the workability of the concrete used in thin slabs is still been investigated.

 

The fibre factor depends on the fibre type, material characteristics, fibre shape, length and diameter. Research is still ongoing but the following table can be used as a guide at this stage:

 

 

Note: If the steel fibres tend to be brittle subtract 0.2 from the factor.