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I am
working on a construction project where we are using steel tunnel forms (5"
wide) that are used to form the finish concrete surface for prison cell
walls. We are seeing a large amount of surface defects (bug holes)
that will have to be patched. We need to eliminate these holes, but
have yet to come up with a good solution. We have adjusted our mix design
several times with changing the quantities and/or types of sand, aggregate,
admixtures, etc....To date, we have yet to find a working solution. We
have also experimented with various types of vibrators. Any suggestions?
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THIS is
a tough one. Sounds like you investigated all the potential remedies.
Have you tried "form vibrators" attached to the steel forms? These will
apply the vibration directly to the area that needs it more. Also
investigate the effect of increasing the proportion of fine materials in the
concrete.
Another approach may be to reduce the size of lifts. If you place
the concrete in smaller lifts - and vibrate each - you may allow the air to
escape upwards.
The best example of bug-hole free (almost) concrete around is founds in
CalTrans projects. I have never checked for their secret, but we know it can
be done. |