Originally Posted By: mkober
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Just because a crack is 3/16" wide does not necessarily indicate that movement of the member is taking place. It may mean that the contractive forces acting within the member have manifested themselves in the form of a very visible crack. Without knowing all of the facts, a calculated guess would be that the contractor did too good of a job applying external heat in one area while the concrete was attaining initial set--causing abnormal shrinkage to take place (although usually, concrete shrinkage is evidenced by a series of narrower, often random cracks in an area). Conditions can be made worse by other factors, such as calcium chloride added to the mix to hasten initial set, forms stripped too soon, and even applying external loads (backfilling the foundation) without temporarily bracing the interior of the walls or waiting until the house framing deadload is in place. Taking a series of non-destructive concrete compression readings in the area of the crack as well as other areas would indicate whether or not the problem is localized in the mix itself. And, yes, cold joints are typically weakness planes, making a logical place to observe cracking if other forces are at work.
Michael J. Kober, P.E. and H.I.
"NACHI Member and Proud Of It!"