[TowerTalk] FW: Concrete Pad for U.S. Tower TX-472

[Matt]

This topic has come up before and I'm sure you will get a lot of answers, but here's mine:

Most conventional concrete mixes will typically achieve about 50% of ultimate strength within 7 days, and will develop about 75% of ultimate strength after 14 days.    To answer your question, I have tilted up many crank-ups 2 and 3 weeks after the pour without any incident.    I would be reluctant to try in only one week.

Since the foundation functions as ballast, the main stresses occur in the vicinity of the anchor bolts, so if you are using a raising fixture, you can actually achieve some pretty good loads on the anchor bolts while in the process of tilting it up.   If you are using a crane or "cherry picker" to pull it up into place, there really is not much load imparted on the anchor bolts.

Hope this info is helpful to you.   Good luck on your project.

Matt
KM5VI



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Chris Wynn via TowerTalk
Sent: Friday, July 24, 2015 10:25 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Concrete Pad for U.S. Tower TX-472

I am in the process of putting up a TX-472.  So far, I have been relatively lucky and things have gone pretty smoothly.  I dug the hole using an excavator and "slightly" over dug it by a few feet.  From my initial calculations, I should have needed just under 8 cubic yards, but ended up pouring 16 cubic yards (32 tons and $2k more)! So far the concrete has sat for 7 days curing in the Georgia sun.  I have been pretty cautious to keep water on it, and covered pretty well. I know that the specs call for that concrete to cure for 28 days.  However, how early can I raise this tower?  Does anyone have any experience with cheating the 28 day curing period?  I was kind of hoping to raise it at the 21 day point. I guess the last real job is to trench from the tower back to the shack.  Therefore, I plan on spending the next couple of weeks burying hardline.....
Thanks y'all and see you in the pile ups!
73's es CUL,
ChrisN4XFA

Christopher L. Wynn
Attorney-at-Law
Christopher L. Wynn, ESQ., P.C.
6716 Church Street, Suite B
Douglasville, Ga., 30134
(770)942-8661 (Landline)
(770)577-1626
chris at chriswynnlaw.com