Formwork Removal Times
Formwork Removal Times
(OP)
Is there a summary guide for the minimum time after which the forms have to remain in place? The contractor asked me the other day if he could remove the forms for grade beam after 24 hrs, the specs say 7 days which seems a bit excessive. Personally I think 3 days should be OK.
Job Location: Greater Chicago Area
Thanks,
Job Location: Greater Chicago Area
Thanks,
Kaiser





RE: Formwork Removal Times
The issue is on the contractor to show that early removal (with lower fc values) is OK with respect to the structure holding its own weight.
With ACI, the forming removal is usually followed by re-shores. I think it is in the early chapters somewhere - 4, 5, or 6.
RE: Formwork Removal Times
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Kaiser
RE: Formwork Removal Times
Other ACI documents, guides to water retain structures and guides to architectural concrete (as I recall), offer more performance based recommendations, with a concrete strength around 1000psi required such that the tensile strength should be adequate to overcome the adhesion of the form.
I find this section of 318 quite challenging, as it presents directions to the contractor within the design code - these must be repeated in the specifications to be taken on by the contractor. Further, this section is often read to imply the contractor needs to provide an alternate structural analysis and model of the building. Using reasonable means of structural analysis to design a shoring system and understanding the strength of the building in concstruction are no doubt the responsibility of the contractor, but attempting to recreate the analysis of the building is dangerous at best and a waste of funds at least.
Refer to section 2 of ACI 301 for further details.
Does your project refer to 301 or do the specifications incorporate similar content?
Daniel
RE: Formwork Removal Times
RE: Formwork Removal Times
Haven't checked in to the forum in a while. Early form removal can also exascerbate water loss from the concrete, which can affect curing. Might be wise to consider application of a curing compound.
Ralph
Structures Consulting
Northeast USA
RE: Formwork Removal Times