Dowels work by spanning the gap across a joint between two panels. They ensure that the two panels remain level with each other at the surface. With the addition of a plastic dowel sleeve, which encloses half of the dowel in one of the panels, the dowel becomes debonded to one of the panels, allowing the slabs to move horizontally in relation to each other.
There are two main types of dowel used today; bar dowels and plate dowels. Plate dowels are more commonly used in new construction and bar dowels are more commonly installed in existing slabs.
For the construction of formed free-movement joints:
The sleeve ensures that the dowel is debonded from the other panel so that there is no restraint to the free-movement joint in the horizontal direction. For the debonding sleeve to work as designed, it must have the capacity for a minimum 10mm of lateral movement in each direction.
In armoured joints, the dowel plate is welded to the joint armour. A dowel sleeve is placed on the dowel on one side, and then both panels can be cast either side of the armoured joint.
If a dowel’s load transfer capacity is exceeded, it is possible that it could burst out of the slab. This is more likely to happen if honeycombing has occurred below the dowel or the dowel is placed too high or too low in the slab section. The shear enhancement of fibre reinforcement is assumed to provide no resistance to this mode of failure.