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Re: Concrete disintegration

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Mike,

The first thing is to take a core sample specifically for petrographic analysis (ASTM C856).  Note that ASTM C856 is actually a collection of many different types of tests of harden concrete ranging from simple visual examination to electron scans.  In order to write a purchase order you need to first discuss with a petrogapher which tests from ASTM C856 would be appropriate for your condition.

When you say the concrete is disintegrating, can you tell if it appears to be in the aggregate or cement paste around the aggregate.  The batch plant could have gotten a rotten batch of aggregate or the aggregate could have been severely contaminated with other material such as clay lumps.  The aggregate could also have a bad chemistry causing after the fact reactions such as alkali-silica reaction (ASR).   If it is in the cement paste it could be several issues such as expired or partially hydrated cement (i.e. possibly bad cement storage practices).  If possible try to find out what type and quantity of admixtures were used.  It is possible they could have been out of date or a certain combination was incomparable.  It is also possible to read .5 oz per 100 cwt as 5 oz per 100 cwt and mess the whole thing up.  I saw this once when the air entraining admixture was off by a factor of 10 and the concrete came out almost like pumice.  You may also want to ask about the source of water.  I have had a couple of bad experiences with river and well water.  If the cement paste appears to be disintegrating from the outside then you may have a severe sulfate problem in the soil.

Thomas Hunt, S.E.
ABS Consulting




"Mike Livingston" <mwlivingston(--nospam--at)hotmail.com>

04/23/2003 01:12 PM
Please respond to seaint

       
        To:        seaint(--nospam--at)seaint.org
        cc:        
        Subject:        Concrete disintegration



Yesterday I told my kids I crushed concrete with my bare hands.  It was less
funny for the homeowners though.  I was called out to look at some homes
where the basement walls and foundations were spalling, slumping, and just
plain crumbling away.  The homes are many miles away from each other with
the concrete supplier being the common factor.  Test cylinders from the same
batch were recently tested with about 1/4 of the strength they had before.
We're going to take core samples, do a chemical analysis, and replace the
foundation, but I'm curious as to what you think the supplier put into his
concrete to have such devastating results a few months later?  (Seems salt
instead of sand might do the trick...)  Does anyone have any reference
materials they can aim me at?
Thanks,
Mike Livingston, SE, CE, P.Eng
mwlivingston(--nospam--at)hotmail.com





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