Stripping Time

In no circumstances shall forms be stnick until the concrete reaches a strength of atleast twice the stress to which the concrete may be subjected at the time of striking.Where possible, the fo~rmwork should be left longcr, as it would assist curing.In normal circumstances (generally where temperatures are above 20%), and where ordinary cement is used, fi,nlls may be struck after expiry of following periods:

a) Walls, columns and vertical sides and beanls 24 to 28 hours

b) Slabs (props left undcr) 4 days

C ) Beam soffits (props left under) 8 days

d) Removal of props to slabs:

i)Spanning upto 4.5 m

ii) Spanning over 4.5 m

e) Removal of props to beams and arches:

i) Spanning upto 6.5 m 14 days

ii) Spanning over 6.5 m 21 days

When concreting is carried out in cold clinlate (where temperatures are 7°C) stripping time will be double, the time mentioned in the above table.

Early formwork removal is not beneficial to the concrete however this may be done on economic ground. Concrete will resist shrinkage cracks better if allowed to dry out slowly and uniformly upto 28 days.Where height of falsework is more than 3 to 4 metre, steel props adjustable or otherwise should be adopted with adequate lateral and diagonal braces.