Preventing "Steps" and Load Transfer

To prevent vertical displacement of adjacent slabs at a joint, some form of load transfer is necessary. This enables the top surface of the slabs to remain at the same level even though they may be subjected to uneven loads. These loads may be in the form of vehicular traffic, or more commonly, as a result of the ground swelling and or shrinking below the slabs. The most effective way to minimise ground swell problems is to provide a firm sub-base and maintain a stable soil moisture content. It is recommended to avoid planting trees adjacent to pavements where possible and maintain plumbing work to ensure the sub-base is not affected by leakages.

It is recognised that saw cut and tooled joints are not effective as a means of load transfer if the joint opens more than 0.9mm. To prevent joints opening by this amount it is necessary to place these types of joints quite closely together. If these types of joints are to be spaced at larger intervals a load transfer mechanism (eg. Dowels) would be required.

The interlocking tongue and groove of the Connolly key joint system provides an effective load transfer for light to moderately loaded slabs over much greater joint openings than either saw cut or tooled joints.

For heavily loaded slabs, it is recommended to provide dowels in all types of joints. If desired, dowels can be used with Connolly key joint by simply removing the pre-formed "knock-outs" and inserting the dowel through the key joint. When used in conjunction with Connolly key joint, the dowels provide the load transfer mechanism and the key joint provides the shrinkage control along with the benefits of having a preformed joint.