[Towertalk] Pouring base of tower

[Jim White, K4OJ]

I think you guys are missing the question....

For self supporting towers, I have seen poured a relatively thin slab 
which is very long and wide...after it is cured a secondary pour is made 
atop the other after a form is constructed and a smaller in square are 
pour is made - but it is usually taller.

Imagine the first pour is a copy of the ARRL Handbook....it sets... a 
form is then constructed on top of it which creates a pour that looks 
like a W4 wattmeter....

Both pours are reinforced concrete with rebar cages and there is a 
common set of rods left sticking up in the center of the intial pour 
which then has a form made about it and that pour made....

When 160 enthusiast  W3IN moved to the East Coast of Florida years ago 
he had time to erect - though not fully energized before his passuing - 
a large self supporting tower which was very wide at the base AND, IF 
MEMORY SERVES - roughly a hundred foot tall... he used this technique - 
the initial pour is kind like a wide footprint and the secondary pour is 
plain old weight.

k4oj

Richard Karlquist wrote:

>>    It should be in one pour so that the base is totally 
>>bonded together. If 
>>the bottom pour has 'gone off' and hardened, you wind up 
>>with two separate 
>>layers. 
>>
>>    Sometimes there are two pours if you have to have two 
>>trucks worth of 
>>concrete but they are poured consecutively with little or 
>>no time delay. 
>>    
>>
>
>So how much delay is tolerable?  It takes me 20-45 minutes
>to drive back to the ready mix place 1 1/2 miles away,
>get reloaded, and drive back.  After 45 minutes, I can
>at least poke a hole in the previously poured cement
>with a stick.  Is this good enough?  Is it helpful to
>sprinkle a little water on the top to slow down the
>curing before the next pour?  Always wondered about this
>stuff.  It is sn't covered in any concrete books I've read :-)
>
>
>Rick Karlquist    N6RK
>richard@karlquist.com
>www.n6rk.com
>www.karlquist.com  
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