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Windows 12-17-2013 06:37 PM

Foundation question - crack with exposed aggregate
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Removed wallboard in the basement to discover something strange in the 90 year old foundation wall. I am not even sure what it is or how concerned I should be. Any help is appreciated. A small crack (1/16") starts on a downward diagonal path from the point where the foundation wall steps down. It proceeds for about 2 feet as a typical crack, and then begins to follow a more horizontal line and more of the aggregate is exposed (mostly solid, a few loose rocks at the surface) and while it continues to follow the sweep of a continuous crack it no longer looks like one. The line of exposed aggregate is 2" wide at its greatest point and 3/4" deep at its greatest depth, and stretches for about 3 feet. At one point a long its length, the wall returns to looking normal (solid appearance, no crack) but then the exposed aggregate appears again 6" further along what would be the projected sweep of the crack. The whole area is covered by efflorescence, and we had trouble in this area one time in the past with water intrusion during a very heavy rain. It was hidden at the time but I am wondering if this is where the water was coming in. It looks as it could have been poured like this, or that water has washed out the cement over the years. I really don't understand why or how that could happen to just one small area, but then again I don't know much about concrete. Any insights and suggestion for fixes are welcome. Sorry for the poor pictures. The hammer is for scale. Thanks for any help.

Msradell 12-17-2013 08:47 PM

That area were the aggregate is exposed kind of looks like a cold joined in the concrete. That could have occurred if the lower concrete started setting up before the other section was poured. It and the small crack are probably nothing to be overly concerned about. Water penetration on the other hand is something that needs to be investigated and resolved. Your best bet may be to excavate that wall on the exterior side and waterproof there.

stadry 12-18-2013 03:49 AM

interesting form pattern - almost looks like block,,, agree - lack of consolidation between conc on top of older conc - poor vibration / rodding is likely the cause of the roughness/honeycombing which's easily fixed once the water's resolved - now would be a good time to insulate bsmt wall, no ?

bear in mind whatever water you stop on the outside HAS to go somewhere so drain it if possible,,, otherwise you're just building a small pond next to your foundation wall :eek: we don' want to hear more leaks 3' OR 20' down the wall

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