The ground beams are designed to be supported by the piles and only the piles. If the clay beneath the ground beams heaves (swells) it should not put significant pressure on the underside of the beam. This is achieved by ensuring a void is left under the ground beam.

To create a void under the ground beams we decided to use a product from Cordek called Cellform. Cellform comprises 2 parts :

• a honeycomb polystyrene base strong enough to hold up the wet concrete that will be poured when the beam is cast but is designed to collapse under higher loads such as when the clay heaves and
• Correx (corrugated plastic) formwork to form the bottom and sides of the formwork.

Excavate between the piles to the required width and depth, crop the top of the piles using a SDS Drill and concrete cutter so that the piles protrude into the ground beams by 50mm. Leave the 12mm bars protruding from the pile top by 480mm.

Place the Cellform in the trenches and fix the reinforcement cages - bending the 12mm pile bars into the ground beam cages.

Deploy a concrete pump to reach those hard to reach places.

And pour.

After finishing, the pump is folded up and washed down.

Elapsed time from piling mobilisation to ground beam concrete pour was 4 and a half weeks.