Building Homes or Extensions/cracks in concrete floor

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Expert: - 5/27/2008


Question
Poured a 6" floor on saturday morning (10am) .Vibrated it.  Returned at 6pm and there was a 2mm approx gap running through it. The floor size is 21'x 15'x 6"deep. The concrete was still fairly soft, Is it possible that crack is only at the top? thanks DAN , ALAN

Answer
It sounds like standard shrinkage cracking.  You didn't talk about rebar.  If the steel was hot it can cause the symptom.  The most likely cause was not waiting for the bleed water to disapate, and trapping the bleed water by finishing too soon.  Concrete doesn''t like ever being more than 12' in any direction without a saw or jointer track at least 1 1/2" deep.  The crack is probably through the slab, though the slab can have good strength and usage.

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Dan Griffin

Expertise

I can answer almost all questions related to the total construction process. My expertise is in commercial construction, though I can field most any residential question. I have hands on experience in concrete, heavy equipment, masonry, all phases of carpentry, interior finishes, and I am fairly strong in mechanical and electrical.

Experience

I have over 20 years experience as a commercial carpenter and commercial construction superintendent. I have another 20 years experience in facility management for a major school district.

Organizations
My favorite hobby for he past 12 years has been singing bass in a The OkChorale men's barbershop chorus and the Mature Moments quartet.

Education/Credentials
I hold a Bachelor's degree in English and Math. I have completed many continuing education hours in the building trades. I hold a Master Carpenter card from the AGC, Associated General Contractors.

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