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Re: Joints in retaining walls

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I have not followed this thread from the beginning, but I thought I would offer my humble observations.

1. It is interesting to compare walls at water treatment facilities (ACI 350) with regular retaining walls (ACI 318). Concrete shrinks and cracks regardless of which code for which the wall was designed.

2. The concrete wall will be tied to the foundation. The concrete foundation will restrain the concrete wall.

3.  The wall will crack due to the shrinkage of the concrete.

4. The thermal expansion and contraction of the concrete wall will be restrained by the relatively constant temperature of the concrete foundation.

5. The foundation for the wall will be in place for several days prior to placing the wall. A lot of the shrinkage (but not all) will have happened in the concrete foundation. The concrete wall (placed on top of the relatively mature foundation) will shrink at a different rate than the foundation. The wall, however, will be restrained by the foundation.

What does it all mean? If cracking is indeed important, look to the ACI 350 to predict the spacing of the cracks relative to the area of the horizontal rebar.

If you provide the proper rebar and joints, you can easily go 100ft joint to joint. But you had better use an isolation joint. You can also use shrinkage compensating concrete, but that takes a bit of experience.

Harold Sprague

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