You know how on the big construction sites,(bridges roads skyscrapers etc.) they always use epoxie coated rebar, because concrete doesn’t adhere properly to rusted steel?
Then why is it when I leave a little Mortar residue in my rusty wheel-barrow, the next day it has become permanently attached?
If concrete stuck to rebar like this we could permanently attach California to the rest of the continent!!
Mr T???
Do not try this at home!
I am a trained professional!
Replies
C'mon T, everybody knows that the regular mix only works on wheelbarrows...ya need the incontinent mix for California...oh, wait, you were trying to save it not flush it, nevermind...
Emily Latello
It's the same rule of nature that dictates that if you try to cover, say a hairline gap between the trim and the wall with paint, it'll never fill it, but if you're painted an antique double hung with gaps large enough for bats to get through, getting anywhere near that gap will seal it shut permanently!
Bob, that same paint that won't hide a small crack, will fill the slots in screw heads so they look like rivets!
TDo not try this at home!
I am a trained professional!
My understanding of the reason for epoxy coated rebar is that the regular will continue to rust until forever comes or until it no longer serves the purpose it was placed there for.
Let's suppose that this is 120 years. Probably acceptable lifespan for most tract homes.
But if a bridge loses half it's strenghth in 50-60 years from rusted rebar - do you want to be riding across it?
Concrete will bond to rusted steel and as long as the bar isn't scaling the bond is probably better than to new, slightly oily steel. Epoxy Coated bar is used when there is a likely chance that chloride migration will reach the bars and begin to react with the unprotected steel. Epoxy coated bars need special handling and if cut or scratched, need to be patched with an epoxy patch kit.
Bridges, parking decks and roadways have significant amounts of chlorides (salt) applied during winter months. Some contractors will add chlorides to concrete in the winter to accelerate setting time and add internal heat during curing. This is bad news for unprotected rebar and post tension tendons.
Concrete really doesn't bond to epoxy coated bars as much as it encapsulates them. If you knock cured concrete off an epoxy bar the contact surface of the concrete is smooth as glass. The deformations on the bar and the hooks or bends lend more to pull-out strength than the actual bond strength.
Eric