On May 18, 7:20*am, RicodJour wrote:
On May 18, 7:57*am, (Doug Miller) wrote:



RicodJour wrote:
On May 17, 8:00=A0pm, (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. *Your personal observation of those funky brown stains on
concrete structures everywhere should indicate that something is
rusting. *If 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. *Concrete is not waterproof. *It wicks up moisture.
The steel doesn't care that it is encased in concrete and will rust in
the presence of the H2O. *Concrete sucks in tension - something on the
order of 1/10 its strength in compression. *Constant tension on
concrete leads to cracking. *Cracking 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-reinforced
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’s 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

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