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RE: Permissible Sulfate Content in Concrete

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Type II and Type V cements are used for moderate and severe sulfate
exposure respectively, however, the key parameter for sulfate resistance is
the water/cementitious (w/c) ratio.  PCA produced a report in 1989,
"Durability of Concrete in Sulfate-Rick Soils", where they tested concrete
samples with varying w/c ratios, cement content, cement type, mineral
additives, etc.  As it turns out, with w/c ratios of 0.40 or less the
cement type has little effect.  For good sulfate resistant concrete you
would be better off with a low w/c and perhaps adding silica fume.  This
can be an important point when performing overseas work where Type II or
Type V cement may not be available or might be very expensive.

Thomas Hunt, S.E.
Duke/Fluor Daniel

----- Forwarded by Tom Hunt/DFD on 01/10/02 08:38 AM -----

                    Harold O."           To:     "'seaint(--nospam--at)'" <seaint(--nospam--at)>
                    <SpragueHO@bv.       cc:
                    com>                 Subject:     RE: Permissible Sulfate Content in Concrete

                    01/09/02 09:49
                    Please respond
                    to seaint

You really need to get some definition on the sulfate concentration.
Sulfate concentrations in soil samples are as follows:
Negligible           0.00 to 0.10
Moderate        0.10 to 0.20
Severe          0.20 to 2.00
Very Severe          2.00 or greater

What is evaluated is the water soluble sulfate in soil as a percent of the
sample weight.  If the guy providing the testing has any experience, he
should have given you the correct data.

You need to look at Sec. 4.3 on sulfate exposure and remedies.

The correlation you ask for does not exist.  The concrete degradation is
time and temperature dependent.  Given enough time, your piles will go away
entirely.  If it is hot, they go away faster.  ...How's that for vague?

You can find commentary and references in ACI 318 Sec. 4.3.  You might also
want to pick up a copy of the Concrete Manual by the Bureau of Reclamation.
They have a good section on sulfate attack.  They should, they are based in
Denver where they have many hot sulfate areas.

If you need any more definitive information, let me know.

Harold O. Sprague

> -----Original Message-----
> From:         John Joman [SMTP:jojoman34(--nospam--at)]
> Sent:         Wednesday, January 09, 2002 11:34 AM
> To:           seaint(--nospam--at)
> Subject:           Permissible Sulfate Content in Concrete
> Here is a question for all you concrete experts out
> there.  I have received some preliminary test results
> from concrete specimens taken from the piles of an
> existing building.  Results indicate that sulfate
> contents range from 0.5% up to 2.5%.  (Not sure if
> this is by total weight of specimen or by total weight
> of cement).  It was also reported that chunks of
> concrete could also be removed by hand at some
> locations.
> I understand that sulfates reacts with the calcium in
> the concrete to slowly degrade the cement matrix.   My
> question is, what percentages constitutes a  mild,
> moderate, and severe exposure?  Chapter 4 of ACI does
> provide maximum permissible chloride contents in
> concrete, is there a similar table for sulfates?  Is
> there any correlation between sulfate content and
> reduced concrete strength (i.e. 5% sulfates equals a
> loss of 10% in concrete compressive strength).
> If anyone can provide some useful references or
> insight into this matter, it would greatly be
> appreaciated.
> Thanks.
> John

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