STEEL FIBRE TECHNOLOGY DESCRIBED

As a rule of thumb, small fibres tend to be used where control of crack propagation is the most important design consideration. High fibre count (number of fibres per kg) permits finer distribution of steel fibre reinforcement throughout the matrix - and consequently, greater crack control during drying process.

On the other hand, because they exhibit better matrix anchorage at high deformations and large crack widths, longer, heavily deformed fibres afford better post-crack "strength". However, unlike shorter fibres, the dramatically reduced fibre count of longer product yields correspondingly less control of initial crack propagation.

PROPERTIES OF REINFORCEMENT

When steel fibres are added to mortar, Portland cement concrete or refractory concrete, the flexural strength of the composite is increased from 25% to 100% - depending on the proportion of fibres added and the mix design. Steel fibre technology actually transforms a brittle material into a more ductile one.

Catastrophic failure of concrete is virtually eliminated because the fibres continue supporting the load after cracking occurs. And while measured rates of improvement vary, steel fibre reinforced concrete exhibits higher post-crack flexural strength, better crack resistance, improved fatigue strength, higher resistance to spalling, and higher first-crack strength.

Figure 1 shows concrete flexural strengths when reinforced at various fibre proportions. Additionally, deformed fibres provide a positive mechanical bond within the concrete matrix to resist pull-out.

Figure 1