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Posted by RicodJour on May 18, 2009, 10:20 am
On May 18, 7:57=A0am, spamb...@milmac.com (Doug Miller) wrote:
> >On May 17, 8:00=3DA0pm, spamb...@milmac.com (Doug Miller) wrote:
> >> How are they going to get bigger while they're encased in concrete?
> >It really surprises me that you have such problems understanding
> >this. =A0Your personal observation of those funky brown stains on
> >concrete structures everywhere should indicate that something is
> >rusting. =A0If you can't see what's rusting, and are keen enough to
> >realize that rust doesn't just magically appear on concrete, you'll
> >probably latch on that the rust is coming from inside the concrete.
> >In a nutshell. =A0Concrete is not waterproof. =A0It wicks up moisture.
> >The steel doesn't care that it is encased in concrete and will rust in
> >the presence of the H2O. =A0Concrete sucks in tension - something on the
> >order of 1/10 its strength in compression. =A0Constant tension on
> >concrete leads to cracking. =A0Cracking allows in more moisture, and the
> >cycle continues until the structure falls apart.
> I guess all those engineers who've been building things with steel-reinfo=
rced
> concrete for all these years must be completely ignorant, huh?
From the results, some of them obviously were.
Your stance is that you can throw steel into a concrete pour and it
doesn't do anything because, hell, rebar is steel. That's like saying
that you can pour gas anywhere into a car since a car runs on gas.
You know, nonsense.
Like I said, if you want to learn, Google the subject. I'll give you
a head start. This is from Wiki on reinforced concrete:
"Common failure modes of steel reinforced concrete
Reinforced concrete can fail due to inadequate strength, leading to
mechanical failure, or due to a reduction in its durability. Corrosion
and freeze/thaw cycles may damage poorly designed or constructed
reinforced concrete. When rebar corrodes, the oxidation products
(rust) expand and tends to flake, cracking the concrete and unbonding
the rebar from the concrete."
And this is from the Canadian Research Council:
"PREVENTING REBAR CORROSION IN CONCRETE STRUCTURES
by Shiyuan Qian
This article reviews the issue of rebar corrosion, discusses some of
the preventive technologies available, and presents information on
recent studies conducted by NRC=92s Institute for Research in
Construction.
The corrosion of reinforcing steel bars is one of the main causes of
deterioration of reinforced concrete structures in North America. It
has become a serious, widespread problem, with repair costs now in the
billions of dollars annually. Whether the corroding rebars are seen
exposed on delaminated bridge decks or
piers, or observed in damaged parking garages, engineers and
contractors are all too familiar with the problem, as are anxious
property owners who call on them to provide solutions."
It's either odd that;
1). these guys are in collusion and making this stuff up
or
2). you've never noticed it.
My bet is on the second.
The main reason that the OP shouldn't throw the scrap iron in the
steps is because it is wasting money. The second reason is that the
random steel "reinforcing" will eventually cause problems.
I'm taking the liberty of cross posting this to some other groups with
more knowledge on construction than this one. Let's see who weighs in
and which way the verdict goes.
R
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Posted by fftt on May 18, 2009, 12:32 pm
> On May 18, 7:57=A0am, spamb...@milmac.com (Doug Miller) wrote:
> > >On May 17, 8:00=3DA0pm, spamb...@milmac.com (Doug Miller) wrote:
> > >> How are they going to get bigger while they're encased in concrete?
> > >It really surprises me that you have such problems understanding
> > >this. =A0Your personal observation of those funky brown stains on
> > >concrete structures everywhere should indicate that something is
> > >rusting. =A0If you can't see what's rusting, and are keen enough to
> > >realize that rust doesn't just magically appear on concrete, you'll
> > >probably latch on that the rust is coming from inside the concrete.
> > >In a nutshell. =A0Concrete is not waterproof. =A0It wicks up moisture.
> > >The steel doesn't care that it is encased in concrete and will rust in
> > >the presence of the H2O. =A0Concrete sucks in tension - something on t=
he
> > >order of 1/10 its strength in compression. =A0Constant tension on
> > >concrete leads to cracking. =A0Cracking allows in more moisture, and t=
he
> > >cycle continues until the structure falls apart.
> > I guess all those engineers who've been building things with steel-rein=
forced
> > concrete for all these years must be completely ignorant, huh?
> From the results, some of them obviously were.
> Your stance is that you can throw steel into a concrete pour and it
> doesn't do anything because, hell, rebar is steel. =A0That's like saying
> that you can pour gas anywhere into a car since a car runs on gas.
> You know, nonsense.
> Like I said, if you want to learn, Google the subject. =A0I'll give you
> a head start. =A0This is from Wiki on reinforced concrete:
> "Common failure modes of steel reinforced concrete
> Reinforced concrete can fail due to inadequate strength, leading to
> mechanical failure, or due to a reduction in its durability. Corrosion
> and freeze/thaw cycles may damage poorly designed or constructed
> reinforced concrete. When rebar corrodes, the oxidation products
> (rust) expand and tends to flake, cracking the concrete and unbonding
> the rebar from the concrete."
> And this is from the Canadian Research Council:
> "PREVENTING REBAR CORROSION IN CONCRETE STRUCTURES
> by Shiyuan Qian
> This article reviews the issue of rebar corrosion, discusses some of
> the preventive technologies available, and presents information on
> recent studies conducted by NRC=92s Institute for Research in
> Construction.
> The corrosion of reinforcing steel bars is one of the main causes of
> deterioration of reinforced concrete structures in North America. =A0It
> has become a serious, widespread problem, with repair costs now in the
> billions of dollars annually. =A0Whether the corroding rebars are seen
> exposed on delaminated bridge decks or
> piers, or observed in damaged parking garages, engineers and
> contractors are all too familiar with the problem, as are anxious
> property owners who call on them to provide solutions."
> It's either odd that;
> 1). these guys are in collusion and making this stuff up
> or
> 2). you've never noticed it.
> My bet is on the second.
> The main reason that the OP shouldn't throw the scrap iron in the
> steps is because it is wasting money. =A0The second reason is that the
> random steel "reinforcing" will eventually cause problems.
> I'm taking the liberty of cross posting this to some other groups with
> more knowledge on construction than this one. =A0Let's see who weighs in
> and which way the verdict goes.
> R
From what I've seen (& read) working in the civil structural field for
since 1988, the major cause of reinforced concrete failure is
inadequate coverage. Followed by poor quality concrete.
Depending on the "exposure" & environmental conditions, as little as
2" of coverage is spec'd, harsher conditons 3"+ or more.
Epoxy coated rebar is a "new, hot" thing but I'm not convinced that it
is "the" solution. Epoxy coating can get damaged during placement,
leaving bare steel. :(
I'll put my money on extra cover and good concrete, designed for the
local conditions.
Rebar that is fully encased in sound concrete with adequate coverage
will last a LONG time.
Too little coverage or poor quality concrete will allow the rebar to
begin to rust....the rusting rebar will "disassemble" the rest;
quickly at first as it attacks the surface rebar but much more slowly
as it progresses to the deeper rebar.
The Huntington Beach, Ca pier (the original one....ca1900) needed to
be replaced due to impending structural failure. One of the
engineers on the project (evaluation of the old pier) told me that IF
the coverage had been adequate, the peir could have been repair and
served another 50 years or more. But due to poor coverage the pier
had to be demo'd and replaced.
cheers
Bob
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Posted by Doug Miller on May 18, 2009, 3:00 pm
>On May 18, 7:57=A0am, spamb...@milmac.com (Doug Miller) wrote:
>> >On May 17, 8:00=3DA0pm, spamb...@milmac.com (Doug Miller) wrote:
>> >> How are they going to get bigger while they're encased in concrete?
>> >It really surprises me that you have such problems understanding
>> >this. =A0Your personal observation of those funky brown stains on
>> >concrete structures everywhere should indicate that something is
>> >rusting. =A0If you can't see what's rusting, and are keen enough to
>> >realize that rust doesn't just magically appear on concrete, you'll
>> >probably latch on that the rust is coming from inside the concrete.
>> >In a nutshell. =A0Concrete is not waterproof. =A0It wicks up moisture.
>> >The steel doesn't care that it is encased in concrete and will rust in
>> >the presence of the H2O. =A0Concrete sucks in tension - something on the
>> >order of 1/10 its strength in compression. =A0Constant tension on
>> >concrete leads to cracking. =A0Cracking allows in more moisture, and the
>> >cycle continues until the structure falls apart.
>> I guess all those engineers who've been building things with steel-reinfo=
>rced
>> concrete for all these years must be completely ignorant, huh?
>From the results, some of them obviously were.
>Your stance is that you can throw steel into a concrete pour and it
>doesn't do anything because, hell, rebar is steel. That's like saying
>that you can pour gas anywhere into a car since a car runs on gas.
>You know, nonsense.
>Like I said, if you want to learn, Google the subject. I'll give you
>a head start. This is from Wiki on reinforced concrete:
>"Common failure modes of steel reinforced concrete
>Reinforced concrete can fail due to inadequate strength, leading to
>mechanical failure, or due to a reduction in its durability. Corrosion
>and freeze/thaw cycles may damage poorly designed or constructed
>reinforced concrete. When rebar corrodes, the oxidation products
>(rust) expand and tends to flake, cracking the concrete and unbonding
>the rebar from the concrete."
>And this is from the Canadian Research Council:
>"PREVENTING REBAR CORROSION IN CONCRETE STRUCTURES
>by Shiyuan Qian
>This article reviews the issue of rebar corrosion, discusses some of
>the preventive technologies available, and presents information on
>recent studies conducted by NRC=92s Institute for Research in
>Construction.
>The corrosion of reinforcing steel bars is one of the main causes of
>deterioration of reinforced concrete structures in North America. It
>has become a serious, widespread problem, with repair costs now in the
>billions of dollars annually. Whether the corroding rebars are seen
>exposed on delaminated bridge decks or
>piers, or observed in damaged parking garages, engineers and
>contractors are all too familiar with the problem, as are anxious
>property owners who call on them to provide solutions."
>It's either odd that;
>1). these guys are in collusion and making this stuff up
>or
>2). you've never noticed it.
>My bet is on the second.
I never said that corroding rebar in concrete couldn't cause a problem -- I'm
simply taking issue with your stand that putting steel into concrete
*automatically* poses a corrosion problem that will necessarily destroy the
concrete.
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Posted by RicodJour on May 18, 2009, 4:31 pm
On May 18, 3:00=A0pm, spamb...@milmac.com (Doug Miller) wrote:
> I never said that corroding rebar in concrete couldn't cause a problem --=
I'm
> simply taking issue with your stand that putting steel into concrete
> *automatically* poses a corrosion problem that will necessarily destroy t=
he
> concrete.
This is what I wrote in my first response to the OP:
"Another reason is that iron has a tendency to rust. When it rusts it
expands. This would put the concrete in tension and concrete really
doesn't like to be put in tension. In other words it would tend to
break up the steps.
Use rocks, brick, or other busted up concrete if you need some filler.
"
I used the words tendency, would, tend to - there is nothing there
that says in all occasions all steel rusts. I also put the rusting
issue in second place in my short list of reasons. You made a massive
assumption that I was somehow referring to all situations and you got
snarky about it.
Your two comments;
"How are they going to get bigger while they're encased in concrete?"
and
"Oh, for heaven's sake. Haven't you ever heard of rebar?"
imply that you equated an engine block dumped in a hole in the ground,
with engineered and correctly installed reinforced concrete. I took
exception to that.
I appreciate that you think the OP - a guy who wants to toss a
considerable quantity of scrap iron into a set of steps as filler - as
being so clued in to the correct amount of concrete coverage, and
would know how to suspend an engine block to insure that amount of
coverage. I have no such illusions.
R
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Posted by bob haller on May 18, 2009, 4:57 pm
> On May 18, 3:00=EF=BF=BDpm, spamb...@milmac.com (Doug Miller) wrote:
> > I never said that corroding rebar in concrete couldn't cause a problem =
-- I'm
> > simply taking issue with your stand that putting steel into concrete
> > *automatically* poses a corrosion problem that will necessarily destroy=
the
> > concrete.
> This is what I wrote in my first response to the OP:
> "Another reason is that iron has a tendency to rust. =EF=BF=BDWhen it rus=
ts it
> expands. =EF=BF=BDThis would put the concrete in tension and concrete rea=
lly
> doesn't like to be put in tension. =EF=BF=BDIn other words it would tend =
to
> break up the steps.
> Use rocks, brick, or other busted up concrete if you need some filler.
> "
> I used the words tendency, would, tend to - there is nothing there
> that says in all occasions all steel rusts. =EF=BF=BDI also put the rusti=
ng
> issue in second place in my short list of reasons. =EF=BF=BDYou made a ma=
ssive
> assumption that I was somehow referring to all situations and you got
> snarky about it.
> Your two comments;
> "How are they going to get bigger while they're encased in concrete?"
> and
> "Oh, for heaven's sake. Haven't you ever heard of rebar?"
> imply that you equated an engine block dumped in a hole in the ground,
> with engineered and correctly installed reinforced concrete. =EF=BF=BDI t=
ook
> exception to that.
> I appreciate that you think the OP - a guy who wants to toss a
> considerable quantity of scrap iron into a set of steps as filler - as
> being so clued in to the correct amount of concrete coverage, and
> would know how to suspend an engine block to insure that amount of
> coverage. =EF=BF=BDI have no such illusions.
> R
ideally all rebar should be non magnetic stainless, which never
rusts.........
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