Concrete Wall Vertical Joints

[marinaman]

I've got a basement wall for a building that is tall, thick, and long.

Its 17' feet tall, 20" thick, and is the basement wall for probably 200' of the perimeter of the building......4,000 psi concrete.

That being said, how do you guys feel about vertical control/Construction joints in the wall, in terms of spacing? I've been playing with 64' in my mind....but then again, this seems to be too close in some ways and too far apart in others.

BTW, there are also cast pilasters in the wall that support steel columns above. The pilasters are to be poured intergrally and are spaced about 32' o.c.

 

[hokie66]

What is the purpose of the joints?

 

[marinaman]

Mainly to aid in limiting the amount of shrinkage cracking that occurs, would be the purpose.

As far as construction joints, I don't know how much concrete the GC will want to pour at one time.....so that spacing, I'm going to see what the GC comes back and requests.

 

[JAE]

So here's a short essay (< 1 page) on using a higher amount of reinforcement to keep cracks under control:

https://www.ascconline.org/Portals/0/Technical-Article-July_WebSC.pdf?ver=2016-07-12-141059-753

Check out ACI 224.3R. That has a lot of discussion on joint spacings in walls.




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[kipfoot]

If the wall will be exposed to view and shrinkage cracks would be objectionable, then I'd consider midway between your pilasters, 16'. If nobody cares if it cracks, then it doesn't matter, but the article that JAE linked suggests that owners do care.

Joints in Poured Concrete Walls

 

[hokie66]

Maybe the ACI 224 covers it, but to be clear, shrinkage reinforcement does not stop cracking, it just controls the width of the cracks.

Shrinkage cracking in not really due to concrete shrinkage, but rather due to tensile stress because shrinkage is restrained, in the case of walls by the footings or slabs which they are cast on.

The 0.6%Ag recommendation in the link which JAE provided has always been my go to provision when crack control of restrained elements is important.

I have no idea why the ACI "shrinkage and temperature" recommendation has been historically related to yield strength of reinforcement, as all steel has about the same modulus of elasticity.