Strength and ductility

It is possible to achieve a compressive strength higher than 400 MPa in CRC, but in order to utilise this kind of strength, it is necessary to provide ductility. Otherwise, the use of reinforcement corresponding to the compressive strength of CRC would result in large cracks even at moderate loads in bending. In CRC this ductility is achieved by the use of small and strong steel fibres. As the strength of CRC is considerably higher than the strength of conventional concrete, the content of fibres is also considerably larger.

This enables CRC to behave in a very ductile manner. An example is the CRC beam shown below, which achieved a centre deflection of 70 mm in 4-point bending. The beam was cycled to full load - a bending stress of more than 300 MPa - 3 times, yet the amount of cracking was minor. All the cracks appeared at the transverse reinforcement.

This means that a strength and ductility similar to that of steel can be achieved in CRC but, as the density of CRC is less than half that of steel, CRC has the more favourable strength/weight ratio. This can in some cases make CRC better suited for long spans, moving structures or cantilevered structures.

Simple joint with 12 mm bars and a width of 100 mm. The beam fails away from the joint.

The use of CRC JointCast for a staircase produced in CRC with 2% of fibres. An otherwise quite complicated joint is made simple but just casting with CRC JointCast and afterwards no sign of the joint is visible.