Re: [TowerTalk] Concrete Base?

[W0UN -- John Brosnahan <shr@swtexas.net>]

At 06:48 PM 11/17/2004, RICHARD BOYD wrote:
> I remember when this discussion came up some years back some professional
> concrete guys told us that the concrete, unless it was an extra wet mix,
> cured to 80-90% of its ultimate strength within 24-48 hours, in reasonably
> dry weather, etc..  That last bit takes a long time but most of the strength
> comes fast.  73 - Rich, KE3Q


Not nearly this fast.  So be CAREFUL.

About 30-35% after 3 days and typically more than 50% after 7 days.
But this is a function of at what point the pour is exposed to air--as 
opposed to
having moisture continuously maintained on the pour.  Not to mention issues 
about
temperature, mechanical disturbance. etc.

For an interesting graph of cure percentage versus when the pour is
exposed to air you may want to check out the following site.
http://www.polysteel.com/manual/manual_04-05.pdf

Most techniques had essentially reached their ultimate strength after
28 days except for a totally enclosed pour where the moisture cannot
escape at all.  This continued to gain strength even after 6 months!

Do a web search and get some real data.  24 hours, even 48 hours is
way too soon to disturb things--something that can greatly affect ultimate
strength.
http://www.uwtc.washington.edu/courses/tc231/documents/StudentexampleRR.pdf

BTW  DRY weather is the worst condition.  You want to keep the pour hydrated
for the chemical reaction to continue for as long as possible.

73 and be safe--John   W0UN



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