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The following table presents the minimum time requirements before removing the formwork. It regards typical constructions for usual temperatures:
| Constructional elements |
Cement strength category |
|
32.5 |
42.5 |
52.5 |
| Lateral sides of beams’, slabs’, columns’, shear walls’ formworks |
3 days |
2 days |
2 days |
| Slabs’ formworks and beam span form-works when the span is lesser than 5 m |
8 days |
5 days |
4 days |
| Slabs’ formworks and beam span form-works when span is equal to or greater than 5 m |
16 days |
10 days |
8 days |
| Safety columns of frame beams and slabs with a span greater than 5 m |
28 days |
28 days |
22 days |
Nowadays, cement with 32.5 strength is usually the cement that comes in sacks. On the con-trary, the cement used by most concrete production industries usually has strength equal to 42.5. When removing the formwork of slab or a beam 5 days after concreting and intending to cast the next floor-which means doubling the loads applied to the floor without formwork - supporting scaffolds (falsework) must be placed beneath the formwork-free floor. This problem is much more critical in cantilever slabs. It must be mentioned that there are a lot of exceptions to the above summarized rules where the suggested limits of most issues may be exceeded. However, in every case the supervisor engineer is responsible for satisfying the general or special specifications of the work.
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« Concrete curing
Self-compacting concrete »
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