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Re: Requirement for control joints in elevated slabs.

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In a message dated 12/11/2002 12:33:32 PM Pacific Standard Time, djkiss55(--nospam--at)juno.com writes:


ACI 224   Control of Cracking in Concrete Structures
ACI 224.1 Causes, Evaluation and Repair of Cracks In Concrete Structures.
ACI 201.2 Guide to Durable Concrete
ACI 207.2 Effect of Restrain, Volume Change and Reinforcement on Cracking
of Mass Concrete



I'm not sure how applicable any of these documents are - a 5 in. slab is certainly not mass concrete.  Also,  these documents are typically addressing concrete slabs, not concrete on metal form deck.  While the cause of cracking might be the same (concrete shrinks as it hardens), the ways of addressing/preventing cracking are not.

If I saw a plan that called for a control joint in a concrete slab, I would assume the designer didn't know what he or she was doing,  I'm not so sure about concrete on form deck.  If the cracking is negative moment cracking over the beams though I would assume it was because there was not enough reinforcing in the slab, that it was too widely spaced or it was at the bottom of the slab, doing nothing.


Gail S. Kelley, P.E.