Removal of Formwork:
The suitability of the materials of the formwork for re-use depends in many respects on the way removal is done. The shuttering boards, frameworks are broken, the smooth surface is damaged and the bracing is bent, if the forms are not removed carefully. Thus, removal of formworks should be carried out in a careful and orderly way. Formwork should not be erased without specific instructions from the engineer-in-charge. The engineer-in-charge before issuing instructions should make sure that the concrete has attained sufficient strength to carry its own load and any other load that it carries at the top. The sides of the formworks, which are not loaded by weight of concrete member, should not be removed before the concrete gains strength. The lateral shuttering is usually removed in summer within 2 to 3 days. Posts supporting the formworks of load bearing structures should be removed only after stripping the sides of the form. Load bearing formworks should be removed only after concrete has gained strength.
The subsequent are the steps for striking the formworks:
(a) Loosening of the tie wires.
(b) Erasing the supports, that supports the formworks
(c) Erasing the shuttering boards or panels.
Under normal circumstances when the temperature is 20oC and the cement used is ordinary, the formwork may be stripped after the expiry to the following periods:
(a) Vertical sides of columns, walls, beams and slabs 1 to 2 days
(b) Beam soffits 7 days
(c) Bottom of slabs
(i) Span of 4.5 m 7 days
(ii) Span of 4.6 m and above, bottom of beams up to span of 6 m, bottom of arch ribs up to a span of 6 m. 14 days
(d) Bottom of beams and arch ribs over 6 m spans 21days