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Re: Cracking in Concrete Slabs on Grade

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I was wondering if I might get some input to a"problem" which has occurred
recently. I designed a 6" concrete slab on grade with control joints at
column locations and mid-bay locations (the column spacing was 25' x 25').
Two days after the slab was poured and control joints cut, the slab cracked
within 1/2" of the control joint. It started at the diamond shaped isolation
joint continued for about 10 feet angled away to approximately 3" from the
control joint for a distance of about 2 feet and then angled back in. On the
other side of the column the crack followed the expansion joint. This
happened approximately one month ago and no further cracking in the slab
(other than where it was supposed to) has occurred. Needless to say, the
owner (it is a moving van storage facility) is not happy since the area will
be subjected to forklift traffic. Can anyone explain why this happened and
if there is another way to repair the area in question besides non-shrink
elastic grout?

Thanks in advance,

Domenic DeAngelo P.E.