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RE: w/c ratio after concrete set

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David,

Petrographic tests will give a back door method to determine apparent w/c
ratios in hardened concrete.  The best approach is sharp special inspectors.
I have had rare occasions where I have had special inspectors at the plant
and at the site to corroborate mix proportions.  It is generally not a
problem.  If a ready mix plant is predisposed to fraud, they will commit
fraud no matter what. 

An unscrupulous ready mix plant could also delete Durapoz, micro-silica,
uniform graded aggregate, use type C ash in lieu of F, use ASR aggregate, or
any other number of things that could not be detected by normal field
plastic concrete tests.

A good finisher will know either immediately or within a couple of hours if
the mix was juiced (too much water) or if they used super-P. 

There are several other advantages of polycarbonate high range water
reducers other than the ability to batch it at the plant. 

The only thing that I know for sure is that the ability to properly batch
concrete, and do the mix submittal correctly is highly regional.  I have
worked in areas where they add air-entraining in all concrete.  It plays
hell for steel trowel finished concrete.  Some regions don't have a clue.
Some regions don't have a problem.  Chicago is one of the best areas.  I
won't get into the areas that are clueless.

Regards,
Harold Sprague

> -----Original Message-----
> From:	David Handy [SMTP:dhandy(--nospam--at)trg.ca]
> Sent:	Wednesday, July 12, 2000 7:39 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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