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
--------------------------------------------
On Tue, 1/12/16, Patrick Greenlee <patrick_g@windstream.net> wrote:
Subject: Re: [TowerTalk] Rohn 25G clone born few minutes ago...
To: towertalk@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@earthlink.net>
> To: towertalk@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
>
> _______________________________________________
>
>
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