[HomrQT]

Originally Posted by harryc

Everything expands and contracts with changing temperature - concrete buildings not so much. All the recent ones I have seen have insulation - even on the slab edges, so probably even less.
Potholes are caused by cars driving over the hole repeatedly, not usually a problem in residential buildings ;-) .

Spalling - where the outer layer of concrete breaks off of the rebar IS a common occurrence, and probably a hefty special assessment. Not sure how much is due to thermal effects, and how much is do to salt+iron => Fe02, for the last 10yrs any rebar that may be exposed to salt has been vinyl coated (green in the photos).

Originally Posted by LouisVanDerWright

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.

Why haven't companies moved to a fiberglass or basalt rebar instead to avoid these issues?