Removing shoring from a reinforced concrete slab

[derecha1]

When is it generally appropriate to remove shoring from reinforced concrete construction. The case I am specifically asking about is a one-way slab supported by reinforced concrete walls. The 7 day breaks have returned at a little over 3,200 psi of 4,000 psi specified at 28 days.

Is there a rule of thumb to go by?

 

[SlideRuleEra]

The South Carolina DOT allows falsework for elevated slabs (typically bridge decks that can be similar to your description) to be removed when test cylinder compressive strength is 75% of design strength. No superimposed loads are allowed on the slab until 90% of design strength. However the specification requires the test cylinders to be cured under the same conditions as the structure (not in the optimum conditions of the testing lab).

This requirement has a long, successful history.

 

[Focht3]

Did you design the slab? If you did, how much of the design load was self-weight, and how much was due to live loads?

I suspect that you're okay as long as you don't allow any imposed loads on it. But this is a call that the slab's designer should make -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[denoid]

I agree with the first two replies. I wouldn't load it with significant live load until the 28 day breaks come in OK.

 

[YSINC]

As a rule of thumb (depending on the mix design), false work for a soffit or walls supporting vert. load should not be removed until the concrete has reached 90% design strength (14-20 days), walls not supporting vert. load can be stripped at 70% design strength (usually around 6-9 days).