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RE: Estimating f'c beyond 28 days

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Re: Design and Control of Concrete Mixtures by PCA or The Concrete Manual by
the US Dept of Interior.

Strength gain relative to time is a function of curing and temperature.
Assuming a moist cure:
	28 days		4000 psi
	56 days		4500 psi
	90 days		4800 psi

Air curing is much more flat after 28 days.  This is ball park based on
percentages from a chart.  Real projected strengths at advanced age should
be determined from testing with a given mix and cement with controls on
curing and temperature.

Regards,
Harold Sprague


> -----Original Message-----
> From:	William Keil [SMTP:WKeil(--nospam--at)TheStellarGroup.com]
> Sent:	Thursday, September 21, 2000 4:37 PM
> To:	'seaint(--nospam--at)seaint.org'
> Subject:	Estimating f'c beyond 28 days
> 
> Assuming that concrete continues to cure indefinitely under certain
> circumstances.  Does anyone have a reference or a rule of thumb for
> estimating the concrete compressive strength based on the 28 day strength?
> So, based on a test yielding 4000 psi concrete at 28 days, what can the
> estimated value at 56 days and 90 days be calculated at?
> 
> TIA,
> William J. Keil, P.E.
> 
> 

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