Posted on 07/06/2016 4:27:17 PM PDT by vannrox
Rust producing moisture and oxygen come from cracks in concrete. Even prestressed reinforced concrete is going to crack over time. Cracks are caused by the loads concrete structures and mats carry, by the tension and compression that can come when concrete members expand when hot and contract when cold, from bending due to wind forces, from vibrations due to traffic or small earthquakes or even noise from close jet engines, depending what and how close.
Moisture is the cause of rust and steel’s enemy. In the past we resorted to galvinizing the reinforcing steel or even coating it with a plasticized coating. Nothing prevents rust, only slows it down.
Since cracks allow moisture access to the steel, cracks are our enemy and if we could only eliminate cracking, steel woul never ruspt or would take a very long time at the least.
One of the most interesting developments in concrete is the possibility for “self-healing concrete” that could repair its own cracks.
http://www.iflscience.com/chemistry/self-healing-concrete-repairs-its-own-cracks/
It is not a complete answer as some concrete may keep repeatedly cracking faster than the concrete could repair, such as high constant winds. But think of bridge decks where various forces cause hairline cracks in the deck. Constant traffic will eventually widen these cracks to where moisture can infiltrate it and ripust the embedded steel, corroding it. Instead of spending millions on bridge maintenance to seal those cracks every few years by hand with a low viscosity Methacrylate seal, if the deck cravks rapaired themselves they would never get wide enough for watervto get in.
Exciting times for technology.
We are not ancient Rome. Rome built everything to last. We build everything to minimize building costs with short design life. I wish we built things much more permanently, but then they would be much more expensive, and many people could not afford them at all.
I know nothing of construction so I didn’t know that either. Very interesting. No one ever thought that rusted rebar would be a problem?
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