Thick Concrete Wall Min Reinforcement

[Boiler106]

I have thick walls used for shielding that vary from 24" to 120" thick and lightly stressed and up to 50 ft long with no control joints.

ACI 350-06 7.12.2.1 indicates a minimum reinf ratio of 0.005, however, there's an exception:

Concrete sections that are at least 24 in. may have the minimum shrinkage and temperature reinforcement based on a 12 in. concrete layer at each face

Does it make sense to reinforce a ten foot thick wall with 24" x 12" x 0.005 = 1.44 in² split between two faces, say #8@12" horiz?

Am I reading this correctly? Is there another reference you can point me to? Thanks!

 

[Agent666]

Will it be poured in one go, is there any chance to have a late pour strip somewhere in the middle after some of the shrinkage has occurred?

One thing to be mindful of in these situations is that the foundation is already there and shrinking/providing restraint to the wall as it's got its own timeline for doing its own shrinkage thing.

I think because you are going from 24" to 120" (a massive change in thickness) there is presumably some regions that are thinner and all of the shrinkage strains will tend to focus their cracking potential in these areas with the lowest tensile strength of the concrete is at the thinnest sections.

I believe in general the temp/shrinkage requirement is one of assuming some sort of distributed cracking being acceptable, but if you are focusing the potential at the thinnest sections you may in fact need more reinforcement at these locations to resist the accumulation of shrinkage that is likely to occur.

You mentioned shielding, if it cracked would it impact on the sheilding? You didn't mention what you were sheilding/protecting from? Not sure if this is an important aspect or not, or forms part of the basis/concern for the question?

Does it make sense to reinforce a ten foot thick wall with 24" x 12" x 0.005 = 1.44 in2 split between two faces, say #8@12" horiz?

Wouldn't make sense to me if the thickness was varying, but in a constant thickness member other codes also have the same provision (AS3600 has something similar (or at least used to)).