Why you don't want rebar to stick out of the concrete is two
fold. First, the continuous moisture contact will cause and
keep the corrosion process going continuously. Secondly,
when reinforcing steel corrodes it expands and will crack
and spall the concrete.
Steel above ground is not continuously exposed to moisture.
It is a cyclical exposure and will take longer to corrode
and is also visible so maintenance can be done. If left
alone it too will corrode and spall / crack the concrete. It
will just take a lot longer all things being equal.
The question of ungalvanized vs. galvanized anchor bolts
boils down to maintenance and the cost there of. Both are
equally strong, galvanized will last longer in a corrosive
environment but cost more. It is a matter of personal or
company preference. Actually the only part of the anchor
bolt that needs to be galvanized is that part that is
exposed out of the concrete.
As far as the rusty bolts are concerned, just before you
install them wire brush off the surface rust and install in
the pour. A yearly visual inspection of the installed bolts
should keep you ahead of any corrosion problems.
As I have posted before, and as Red says, don't weld rebar
unless you are using ASTM A706 bars or are using the AWS
preheat procedure for standard bars.
Lonberg Design Group, Ltd
H.S. Lonberg, P.E.,S.E. / KR7X
[mailto:firstname.lastname@example.org] On Behalf Of Rick
Sent: Friday, July 07, 2006 2:59 PM
Subject: Re: [TowerTalk] Welding re-bar, preventing
> It is important that no steel penetrate the concrete below
> penetration provides a path
> for the natural alkalinity of concrete to leach out, thus
losing some of
> the anti-corrosion
> protection that concrete provides to steel. Bring
grounding terminals out
> of the concrete above
Let me make sure I understand this correctly. A piece of
poking out of the concrete below grade will rust. A piece
steel poking out above grade will not rust? Why is this?
moisture related? The stuff above grade will still get wet
whenever it rains or there is dew.
This brings up the question of anchor bolts: galvanized or
steel? I notice that UST supplies non-galvanized bolts.
every streetlight I've seen uses galvanized bolts.
what you say, the black steel is OK on account of it being
grade. Right? I noticed that the UST bolts are already
when you get them from UST, not to mention what happens
after the first
rain. Any advice here?
> To prevent penetration, place concrete "pills" at least 3"
> under the steel at the
> bottom before pouring the concrete.
When you go to the store, ask for "dobies" not "pills"
(and not "doobies" either :-)
> 73 de WOØW
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