The inclusion of steel fibres in concrete slabs for shrinkage crack resistance is inherently inefficient due to their random orientation through the slab depth. This paper describes the development of a prototype device which has been used successfully to align the fibres onto a horizontal plane at a chosen depth below the surface, using compact permanent magnets. A fin, housing the magnets, is attached to a vibrating screed and is dragged through the fresh concrete. The various conflicting design parameters are discussed in detail, including the choice of magnet, fin and concrete workability requirements. The effectiveness of using this device is evaluated and perceived potential benefits are identified.

  • BACKGROUND: REINFORCING FLOOR SLABS ON GRADE

  • ALIGNMENT OF STEEL FIBRES USING PERMANENT MAGNET

  • ENGINEERING ISSUES

  • CONCLUSIONS

  • ACKNOWLEDGEMENTS

  • REFERENCES

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