CRC JointCast

The combination of high strength, a large silica fume content and fibre reinforcement provides CRC with exceptional bond properties, which are utilised in a product called CRC JointCast. CRC JointCast is used for in-situ cast joints between pre-cast elements in conventional concrete. As full anchorage of a reinforcing bar can usually be achieved with an embedment length of 5-8 bar diameters after only 3 days, CRC JointCast can provide small and simple joints that have full moment resistance and considerable ductility.

A number of different types of joints have been tested and for bar diameters from 8 mm up to 51 mm. The system was first used to connect slabs for a new building at Aalborg University. In this case a column/flat slab system was used where the columns were placed in a 6x6 m grid. This could have been done with an in-situ cast slab, but in order to take advantage of the flexibility and speed of erection of using elements a system was developed where pre-cast 3x6 m slabs were joined with CRC JointCast in the middle of a span and over the columns.

CRC JointCast is used where it can provide a solution that is better, faster or cheaper and preferably all of those. Examples could be where traditional joints are much too complicated or too expensive, or where the possibility of having a full strength joint in 3 days can be used in the building process. Yet another application is in seismic areas, as the joint is often the weakest part in precast buildings. With CRC JointCast the joint has sufficient strength and ductility to avoid failure in this area.

Traditional joint on top with looped bars and a number of transverse bars. CRC JointCast joint shown below. Both joints are with 16 mm bars. This type of joint - with permanent shutters - is used for bridges.

End of bridge slab joint with 20 mm cover to the rebars at the bottom

Detail of the joint prior to casting. The rebars were mounted with strain gauges for testing purposes.

Pictures showing CRC JointCast used. The 100 mm wide joints are stronger after 3 days than the slabs, which means that failure will never occur in the joints.