Quote:
Originally Posted by Blahshead
I have a general, off-topic question I thought of while looking at NEMA:
Do concrete buildings expand and contract in the winter/summer months? Can they get "potholes" or erode the way roads do?
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As Harry says, spawling is a major maintenance issue with concrete structures. The issue is that, no matter how well you coat or bury rebar, iron will rust when oxygen reaches it. That wouldn't be an issue except that oxidation of iron results in it gaining two oxygen atoms which means it is actually gaining mass out of the air and more mass means it takes up more space which means it expands and eventually shatters the concrete around it.
This is fix by continually repairing any cracks or spawling that is occurring to limit the amount of oxygen reaching the rebar as much as possible.