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RE: W/C ratio

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Read the references and studies of Jim Shilstone, David Whiting, and Robert Ytterberg.  There are several tests with varying water contents, cement contents, w/c rato's. There was little difference in drying shrinkage.  

If you would like other references, look at 2 additional studies one PCA work by Gebler and another ACI SP-68 study by Rixom & Waddicor.

Now if we are talking plastic shrinkage, that is different topic. And the higher water contents do make a difference.

The high levels of drying shrinkage of grouts are not due to w/c ratio's.  The high shrinkage is more due to the lack of large or uniformly graded aggregate.  Aggregates do not shrink.  Drying shrinkage takes place in the cement paste.  

The high range water reducers also reduce the amount of cement in a given mix which reduces drying shrinkage.  The w/c ratio is not the issue, the amount of cement paste in the concrete matrix is more the issue.  

Harold Sprague

-----Original Message-----
From:	Scott A Jensen [SMTP:SAJ5(--nospam--at)]
Sent:	Tuesday, June 09, 1998 9:03 AM
To:	seaoc(--nospam--at)
Subject:	RE: W/C ratio

I agree with Mr. Sherman.  The amount of water has a great affect on
shrinkage.  This is particularly true for high slump grouts.  My experience
with high slump grouts has been that the use of high range water reducers
greatly decreases the shrinkage.  I have seen grout mixes (water, sand and
cement) with shrinkage as high as 4% .  The shrinkage was reduced to less
than 1% by the use of high range water reducers and significant reduction
in the water used.   The examples Mr. Sprague gave have approximately the
same water content.  Therefore, the shrinkage should be about the same.

I agree that different w/c ratios can have the same shrinkage.  I agree
with Mr. Sherman's statements.