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[TowerTalk] Concrete Strength

To: <>
Subject: [TowerTalk] Concrete Strength
From: (
Date: Mon, 19 Mar 2001 17:52:55 EST
In a message dated 3/19/01 2:18:48 PM Pacific Standard Time, writes:

> I am putting up a US Tower TX-455 in about 4-6 weeks.  When I priced the
>  concrete delivery, the first question was; "What strength do you want?"
>  Examples given were 1500 lb., 2000 lb., etc.  I asked a US Tower
>  representative, but they didn't know.  Any recommendations from the list
>  would greatly be appreciated.

    Okay, concrete. According to the US Tower Foundation Notes - General, it 
calls for "minimum compressive strength of 3,000 psi @ 28 days". This is 
pretty a typical contractor-type mix. On the foundation drawing notes it 
calls for 2500 psi. Take your pick. 

    Here's something that I'm trying to change in regard to US Tower 
installations. It's almost impossible to dig some of the holes that are on 
their drawings and in their catalog. For example, your tower in the catalog 
calls for a 3' x3' x 6'6" deep hole. This is impossible for a backhoe to dig. 
There's not enough room to articulate the bucket and do the excavation. You 
can't dig it by hand; not only is it dangerous but also there's not enough 
room to use a shovel. I don't think anyone from UST has actually installed 
one of these bases - it's really a stupid design. My advice is to get an 
engineer to design a more "practical" configuration. 

    I always try to get the anchor bolts and base fixture sent a month or so 
ahead of the tower delivery so that you can install them and allow a couple 
of weeks for concrete curing. Then when the tower arrives, you have a 
boomtruck or backhoe meet the truck and unload the tower and then carry the 
tower over to the base and drop it in place. This way you only have to have 
the boomtruck/backhoe to show up once instead of twice. 

    You can either make a wood template to hold the anchor bolts in place 
while you're pouring or weld them together with some rebar. In both cases, 
you're trying to hold the anchor rods in the proper alignment during the 
pour. Either tie the rods to the rebar cage or space it above the forms with 
a 2x4 under the base fixture.

    It's a bunch of work but it'll be worth it. Drop me a line if you've got 
any more questions - I've installed a number of these and other towers. 

Cheers, Steve     K7LXC
Tower Tech 

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