need help deciding between expansion joints or relief cuts

[newbietocement]

I am pouring a monolythic floor with a 4" slab floor that will be 24'x40' and I have only used expansion joints in previous slabs but have been told to cut in control joints instead, I am not familiar with this as all of my jobs have been small home projects. any suggestion?

 

[concretemasonry]

Why use an expansion joint in a "momolythic" concrete slab? Do you have extreme condtions?

For crack contol in a slab you can either saw in a control joint about 1/3 of the depth or have a joint tooled.

If it is a pavement, you may widh to install a "dowel box" or similar to transfer shear. Doubtful with a 4" slab.

Depending on the use of the slab, I would cut the 12' width in half and the 40' length in thirds if I was using WWF.

 

[shin25]

You probably can eliminate contraction joints entirely if you provide .006*Ag reinforcement.

 

[csd72]

Sawn joints are so much cheaper than expansion joints and work well as long as they are cut when the concrete is still green.

This slab is tiny and I agree that an expansion joint would be overkill.

To put things into perspective, in industrial slabs, we used to put sawn joints at maximum 30' centers and expansion joints (or similar) at 60 to 100' centers.

In your situation I would put the sawn joints much closer.

csd

 

[COEngineeer]

I usually put expansion joints at the end of the slab(but up againts foundation wall). The control joints is for crack so if it does crack in the future, the slab wont look ugly. Good luck!

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Sea Water Intake and Jetty Construction

 

[csd72]

COEngineer,

What stops the foundation walls moving inwards under soil loads then?

csd