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Crumbling concrete

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I'm curious what would cause older concrete walls to crumble into a lightweight, easily-friable condition.

Here's my story:

I just went by a 100+/- year old residence yesterday and saw the most amazing concrete wall deterioration I've ever seen. Portions of this mostly-above-ground basement wall (I'm going to say 30-50%) were friable to the touch, and easily (literally fell apart) crumbled in my hand. In the soft areas, a masonry bit advanced without significant resistance until it hit a large piece of aggregate, usually about 1.5 to 2" into the 9" thick wall. My only time reference is that - according to the owner - it wasn't present in the 60s when they bought the place.

There is significant evidence that some organics were included in the mix, along with sand and round river rocks. You can see the diagonal striations of segregation from where the concrete batch placement started at the corners and flowed down the walls to its final resting place. I'm guessing that casual water intrusion has slowly decayed the organics to the point that they have partially disintegrated reducing the strength, with the remaining organics moisture cycling to break what was left. There was no obvious sign of chemical residue on the surface of the wall.

Interestingly, there is no sign of macro-deterioration of the structure (yet). No settlement or stress cracks, even where the unbalanced backfill is close to 5 feet. Nonetheless, the walls are going to have to be replaced.

I'm curious what might be happening, and if there are any tests that might be recommended to determine the cause of the damage. I'm doing this as a side research (unbillable) for future reference, as the current owner just wants to know how to fix the problem (replace the walls), and the value of the house is only about $120k-$130 without the wall issue, and currently has no historic significance.

If you're curious, there are some photos here:

http://www.truesdellengineering.com/1125/index.html

Thanks, in advance, for any thoughts/suggestions you folks might have,

Jordan



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