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RE: W/C ratio, was:purposely permeable concrete

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If it is permeability that drives the w/c specified, use of silica fume
(aka microsilica) admixture would greatly reduce permeability.

> ----------
> From: 	Jeff Smith[SMTP:smthengr(--nospam--at)]
> Sent: 	Monday, June 08, 1998 10:14 AM
> To: 	seaoc(--nospam--at)
> Subject: 	W/C ratio, was:purposely permeable concrete
> On a similar subject, I am working on a job where the soils engineer
> required a concrete water cement ratio of .45 for slabs on. Basically
> this
> means you end up with a 5000 psi or more mix unless you substitute
> additives
> in lieu of more cement. Locally, the additives costs at least as much
> as the
> cement. The slabs only need to be 3000 psi for structural reasons. I
> believe
> the w/c requirement is for permeability reasons. Has anyone had a
> similar
> experience with an economical work around?
> Jeff Smith