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The timing of removal of formwork will depend on the rate of strength gain of the concrete:
(a) Vertical surfaces can be struck when the concrete is strong enough to resist the adhesion on the concrete/form face surface.
(b) Soffits cannot be struck until the concrete has gained sufficient strength for the element to support is self weight for all or part of the structural span.
It is possible to speed up the removal of much soffit formwork by removing a small part of the formwork and then installing props to this area. Another area of formwork can then be removed and props installed props. This sequence can be repeated until all the formwork has been remove and the soffit is fully propped.
When removing formwork it is important to avoid damage to the surface of the concrete and particularly to edges and corners. Following removal of the formwork, all exposed surfaces must be covered with polythene or wet hessian to prevent moisture loss for about 5 days, so that the concrete is fully cured.
Guidance maybe found in two leaflets from The Concrete Society, Checklist for erecting and dismantling falsework and Checklist for the assembly, use and striking of formwork, and in the CONSTRUCT A guide to the safe use of formwork and falsework.
Acknowledgement: The Concrete Society
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