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Fwd: Re: Concrete in Salt Water Environment

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It is absolutely astounding to me that on a glorious sunny California day,
 so many of us would be reading this newslist and responding so quickly,  on
 Palm Sunday to boot!!!

My 2 cents from experience at the Port of Oakland where we had about 20,000
piles built/maintained is you're on the right track with the (1) lower w/c
0.4-0.45.  use o.4 if possible.  (2) higher strength concrete 6000 psi or
greater helps;  The combination will help minimize the microcracks for
water/chloride penetration (3)  epoxy coated rebar as an additional layer of
defense is still recommended,   but only with vigorous inspection.   You have
to find the right inspector or R.E. willing to shove the contractor back on
the inevitable nicks and dings on the coating.  Otherwise,  it is a waste of
money  (4) 2.5" cover is minimal.   At the Port,  we used 3" to provide more
cover to protect the rebar.  the additional depth also provides a greater
degree of latitude for construction bloopers. (5)  lastly,  the sacrifacial
anode is a good alternative / backup to a hard-wired cathode protection.
 Just have to remember to replace the metal every couple of years.  My 2cents

Ron Fong
Fremont,  Calif.

In a message dated 97-03-23 09:51:44 EST, you write:

 Dear List Members:
 We are involved in designing some structures that are for use in a
 research laboratory for marine environment (salt water).  This is here
 in the US, and is in an area where freeze-thaw cycle is not an issue
 (Santa Barbara).
 I am in a quandary as to what to do with the reinforcing steel.  We are
 going to use type V concrete, cover all steel with 2.5" minimum cover,
 use a strength of concrete in the range of 5000 to 7000 psi, and use a
 low W/C ratio (around .45)
 We are also going to be using a carefully selected source and gradation
 for our aggregate, to get a high density, low permeable, low reactive
 mix.  We are considering using some of the admixtures that increase the
 density of the mix.
 From what I have read, the issue listed above are pretty much agreed
 upon by most professional in the design of concrete for a seawater
 environment.  However, as I read studies and articles, there is a big
 disagreement on what should be done with the rebar.  Epoxy coating,
 galvanizing, other treatments to rebar, and just using normal untreated
 steel seem to have their supporters and critics.  It seems that plain
 old steel without any treatment may be the way to go, if you use a good
 high density mix with plenty of cover over the rebar.  I am leaning in
 that direction, but the Owner (State of Calif.) seems to think that we
 should do something to the steel, and they do not feel comfortable
 without some kind of treatment to the steel. 
 If someone who has had experience in this area could comment on what
 their views are, I would really appreciate it.  I have read many studies
 and articles in Concrete publications (ACI, etc.), but there does not
 seem to be a consensus on this issue.

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Richard Lewis, P.E.
Missionary TECH Team

The service mission like-minded Christian organizations
may turn to for technical assistance and know-how.