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RE: w/c ratio after concrete set

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David,

Pardon me if I'm outa line here but isn't w/c ratio directly correlated to
design mix strength ?  If your w/c ratio is getting thrown for a loop
somewhere it will definitely show up in the compression test results.
Additionally, if they've submitted data in accordance with ACI 301 you
should know the design average strength and the running standard deviation.
Am I missing something ?  No mater what admixtures are added you should have
some past test results to go off of.

Robert C. Rogers, PE
robert.rogers(--nospam--at)woolpert.com


-----Original Message-----
From: David Handy [mailto:dhandy(--nospam--at)trg.ca]
Sent: Wednesday, July 12, 2000 8:39 PM
To: seaint(--nospam--at)seaint.org
Subject: w/c ratio after concrete set


Is there any way to test, ie. petrographic testing, the quantity of w/c
ratio after the concrete slab has cured. I am thinking about amount of
porosity or bleed channels or so on?
I ask this because I am trying to ensure that the water/cement ratio as
spec'd is what we get on site. We can ask for batching tickets to see if
that matches. What if the supplier adds a pile of water or ice after the
fact in order to meet slump requirements instead of the super-p that is
added at the plant. 
Harold S. mentioned this newer type of super-p (polycarboxylate) that is
added at the plant and maintains the high slump while being agitated. We
used to spec a very low slump concrete and we would add the super-p on site
to get to 5" or 6". If the super-p is added at the plant, they could add
more water and add less super-p. The slab then cracks all to hell and then
how can we prove we did not get what we asked for? 
I have come across too many truck drivers, who after repeatedly being told
not to add water, add water and act like they have never heard of this rule
before.

David Handy, P.Eng
Ontario, Canada

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