|Subject:||Re: [TowerTalk] Concrete Base?|
|From:||W0UN -- John Brosnahan <firstname.lastname@example.org>|
|Date:||Wed, 17 Nov 2004 19:21:26 -0600|
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
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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