[TowerTalk] Rohn 25G clone born few minutes ago...

[J. Hunt]

Thank you Patrick

I am not a concrete engineer either, but always will exercise on the cautious side.  Your notes are very good.

Hopefully within 2 weeks I will be starting tower #2 on my property.
Currently North Texas is over-saturated with above average rain-fall.
The tower base hole will be dug once the soil dries up some and allowed to additionally dry out more prior concrete pour.
Due to the reduced temperatures and higher moisture, I plan on a >45 day cure time. 

James

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On Tue, 1/12/16, Patrick Greenlee <patrick_g at windstream.net> wrote:

 Subject: Re: [TowerTalk] Rohn 25G clone born few minutes ago...
 To: towertalk at contesting.com
 Date: Tuesday, January 12, 2016, 8:08 AM
 
 The rule of thumb is 28 days to achieve 90% of final cure strength but  this is modified by temperature of the air and ground, sunlight,  available moisture (do you mist the surface frequently the first day or  two if ambient temps are high), any additives to speed or slow the cure,  and so on. Here in Oklahoma my PE soils engineer consultant supervised a  pour done at 0200 local and within an hour or so they spread tarps over  the surface and flooded the pour to a depth of a couple inches with  water to reduce heat buildup. This was a quite large commercial building  floor slab thickened in areas of loading.
 
 Caution doesn't hurt in deciding when enough is enough, especially for  hobby projects as a wait period likely is not costing BIG BUCKS EVERY  HOUR. You can't wait too long but you can wait too little. I prefer to  err on the side of caution (but  not ridiculously so.) Consider the  ramifications of "messing up" the concrete and "losing" whatever you  stuck into it, physically and monetarily.  Compare that to the, perhaps  anxious wait of a few days.
 
 In my personal concrete work I try to go by the book as to incremental  cure strength, never approaching too close to the limits with my loading  and then toss in a little extra wait time because I don't want to "mess  up" and incur all the associated negatives of the downside.  I am not a  concrete professional but I do own 3 cement mixers, two electric and one  PTO powered for the 3 point hitch on the tractor and I admit to pouring  way more concrete than the average bear.
 
 My best advice is to take all the extant factors into consideration and  add a safety margin that makes you feel comfortable.
 Remember all the  outside advisers and their opinions, including mine, are not connected  to any liability so don't let any of us get you into trouble.
 
 Patrick        NJ5G
 
 
 On 1/11/2016 11:08 PM, DALE LONG wrote:
 > For most purposes 7-10 days should be enough to begin building a tower.  No need to wait one month unless you are building a monster tower.
 > Dale - N3BNA
 >   
 >
 >        From: Ed Sawyer <sawyered at earthlink.net>
 >   To: towertalk at contesting.com
 >   Sent: Monday, January 11, 2016 11:12 PM
 >   Subject: Re: [TowerTalk] Rohn 25G clone born few minutes ago...
 >     
 > Congrats Douglas!
 >
 >   
 >
 > The Concrete manuals say that concrete will reach 75% of its 28 day rated strength in 7 days.  Almost 90% in 14 days. 
 >  For tower building, 14 days is already overkill.  7 days is plenty. Obviously, the other question is what
 > was the specified mix strength.  If you have 5000PSI concrete, then its already stronger than typical building foundation
 > concrete after only 7 days of cure.
 >
 >   
 >
 > Ed  N1UR
 >
 > _______________________________________________
 >
 >