Fracture energy test on notched beam

Loading of CRC beam

The extreme ductility observed in CRC - in beams, slabs, joints and columns - is obtained by having a large content of small steel fibres and closely spaced main reinforcement.

The graph shows a comparison between two notched beams loaded in bending. The red curve is for a beam with no fibres, while the blue curve is for a beam with 6% of fibres. The energy under the blue curve is 100 times as high as the energy under the red curve, which means that the resistance against development of cracks is much larger with the fibre reinforcement.
The effect of this can be observed in the picture, where a 2 meter beam - the one described in basic principles - is loaded in 4-point bending. Center deflection is 70 mm and bending stresses are higher than 320 MPa.  

While more typical CRC structural elements are not loaded as heavily the beam demonstrates how the ductility of CRC allows very large deformations - and thus ample warning - before failure occurs. The large fibre content helps control the crack width of any cracks.

Article in Concrete Engineering International

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