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RE: Calcium Chloride in Concrete

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I would recommend reading "Factors Affecting Use of Calcium Chloride in
Concrete", by Homer Lackey, 1992, ASTM.  There was a long history of calcium
chloride use for all structures prior to the late 70's and early 80's.  Then
all the bridges, parking structures, etc. started coming apart and calcium
chloride got the blame and was exiled.

But upon reflection there were other causes: poor detailing, insufficient
rebar cover, carbonation, external calcium chloride sources, porous
concrete, and other corrosion factors in the concrete mix design.

Once calcium chloride was made the culprit for concrete's ills, the
admixture people fanned the flames and stepped up providing non-chloride
accelerators.  But the cost increase was significant and the performance was
not as predictable.

As an example of structures containing calcium chloride, look at the
Kaufmann and Arrowhead Stadiums in Kansas City that were constructed in the
early 70's.  These structures had calcium chloride added.  Areas were just
recently topped with a membrane due to isolated corrosion, but the structure
is generally performing very well after almost 30 years of service.

If you took that same concrete and built a parking garage or bridge, you
would have had major repairs or replacement by now.

In general, small amounts of calcium chloride is a cheap accelerator for
winter construction.  If you stay within the limits of ACI 3.6 and 4.3, you
will have no problems.  Check the mix design submittal and see if you are
within the parameters of ACI.  If you are, your concrete should perform
well.  As a caveat, all ingredients need to be checked as outlined in 4.3.

The judicious use of calcium chloride is common in many areas of the U.S.  

Regards,
Harold Sprague
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Fountain Conner [mailto:fconner(--nospam--at)gulf.net]
Sent: Wednesday, January 06, 1999 12:28 PM
To: structx(--nospam--at)mLists.net; seaint(--nospam--at)seaint.org
Subject: Calcium Chloride in Concrete



Have I fallen from the train?

I have never allowed Calcium Chloride in any of my concrete.

But contractors and concrete suppliers in this area (we sometimes have some
low temperatures), will use it without even asking.

Has concrete chemistry changed so that calcium chloride is no longer
harmful to concrete and/or rebar?


Fountain E. Conner, P.E.
Gulf Breeze, Fl. 32561