Concrete Shrinkage - Slab on Deck

[Drgray1]

I am pouring a slab on deck. Do I need to allow for shrinkage, of the thickness? I want a final thickness of 4", to match up with beams that will be flush with top of concrete.

 

[JedClampett]

Shrinkage is a very small percentage effect that is only important in the long dimensions of concrete slabs. Your four inch thick slab will shrink insignificantly through its thickness.