W7CE w7ce at curtiss.net
Mon Aug 28 21:24:47 EDT 2006

>I would say one week is not enough, remember the compression/tension from a
>tower in wind is a lot more stressful than foundations.  I think you are
>guessing, the people who poured my concrete said they always recommend 3 to
>4 weeks for towers or longer for complete curing.

The compressive strength of concrete is always based on 28 days of curing 
time.  If you specify 3500 PSI concrete, it will take 28 days of curing to 
reach that strength.  After 28 days, it will continue to get stronger. 
After 7 days of curing it will only have reached about 60% of its 28 day 
strength.  If you were to install your tower before the 28 days has elapsed, 
it is possible that the concrete could be weakened by the premature stresses 
that the tower puts on it.  This may or may not be visible by inspection. 
Do what the manufacturer says.  Let the concrete cure for 28 days minimum, 
and be sure to keep it wet during the curing process.  Cover it with burlap 
or black plastic and don't let the surface dry out.  In spite of all 
anecdotal evidence to the contrary, play it safe and do it right.  It's only 
4 weeks.

Clay  W7CE

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