Diamond Dowel system produced by Permaban

Diamond Dowel has revolutionised and simplified the traditional method of providing load transfer between adjacent slabs using dowels.

Permaban have been at the forefront of floor design, installation, product manufacture, floor repair, maintenance and aftercare for 25 years.

Since being founded in 1983, Permaban have become a leading supplier in the UK, Europe and Middle East with new presence in Asia.

The product range offers quality solutions for Leave-in-Place joint systems, Dry-shake floor toppings and concrete curing and joint sealants.

Permaban's Regional Sales Manager, Andrew Mackenzie explains the introduction of the Diamond Dowel system produced by Permaban Limited.

Following it's development in 1999, the Diamond Dowel has revolutionised and simplified the traditional method of providing load transfer between adjacent slabs using dowels.

Traditional round dowels have been and still are the most common method of providing load transfer across free contraction joints.

Most engineers appreciate that using round dowels allows shrinkage contraction in one direction only.

Round Dowels do not permit any lateral movement of the slab, resulting in the slab 'locking' and cracking across the corners.

The introduction of the Diamond Dowel followed research carried out for the American Concrete institute publication on floor slab construction.

The Diamond Dowel Investigation included the development of extensive computer programmes to analyse the Diamond Dowel as a finite plate element on a elastic foundation.

The analysis demonstrated that the stresses reduce significantly beyond the first 25mm of the dowel beyond the joint line.

Thus the shape of the dowel can be used to optimize the effective use of material for load transfer.

The 6mm thick, 110mm sides Diamond Dowel shape is used on ground supported new construction floors (both indoors and outdoors) up to 250mm thickness.

For over 250mm thickness, jointless slabs or piled construction a thicker dowel plate (10mm AD10 Plate Dowel) was designed to transfer the larger loads involved and allow for extra movement.

This type of dowel has a trapezoidal shape.

The diamond or trapezoidal shapes of these dowels give lateral movement capability once the initial normal shrinkage occurs but is further ensured by the plastic sleeve.

The sleeve is nailed to timber formwork and cast into the slab.

When the timber is stripped a flat vertical face of concrete is revealed with slots ready to receive the respective steel dowel plates.

The sleeve has plastic lugs which centre the plate dowel and break in the event of pressure.

Thus lateral and even compression movemement (such as could occur if being used for an expansion joint) will break the plastic lugs rather than stress the concrete.

"The Diamond Dowel system has been used for load transfer in the free contraction joints on virtually every large distribution centre built in the UK during the last five years".

"The Diamond Dowel System costs less than conventional sleeved round dowels.

explains Andrew Mackenzie.

To conclude, the Diamond Dowel has significant reserve strength because the plate can re-distribute the stresses if local yielding occurs.

The diamond plate is the optimum shape for a dowel; it is wide where the bearing, shear and flexural stresses are highest and is narrow where the stresses are reduced.

Importantly, the Diamond Dowel allows the slab to move in two directions on the horizontal plane without the restraint, as the concrete shrinks and the joints open.

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