[TowerTalk] Tower bases and concrete.

Bill Coleman aa4lr at arrl.net
Fri Mar 24 07:48:24 EST 2006

On Mar 24, 2006, at 5:42 AM, Robert Thain wrote:

> I am going to install my first tower. But I know
> nothing about concrete.
> What ratio of concrete to sand do I need ?

You don't mix sand into concrete.

Concrete is a mix of a filler material, known as an aggregate, and  
cement. The aggregate is usually a gravel or other rock. Sand helps  
to fill the spaces between the gravel. For something like a sidewalk,  
the top layer is all sand (called a "sand mix") which allows the  
surface to be very smooth.

> Are there differnt sorts of concrete and sand ?

Yes. Your tower base should use a regular mix, with perhaps a sand  
mix on top, if you want a very smooth top of the base.

> Are
> there any special things I should add to the mix ?

You can add additional cement for a stronger mix. There are also  
fibrous fillers that add string.

> Does it differ from country to country ?


> I had thought about 'bulking out' the mix by adding
> big rocks. If I have a 2mcube hole and I add 1mcube of
> rocks, I then only need 1mcube of concrete. Is this a
> good idea ?

You need a very qualified rock. Rocks that are weak and frangible  
will weaken the concrete. Rock that has much embedded water may also  
cause a problem by freezing and cracking the base.

> I find these rock very heavy for their size, roughly
> the same weight as concrete. I also have some old
> concrete slabs I could add.

Small chunks of concrete make good aggregate.

> Also I would like to set some beverage posts in a
> small concrete hole, would this be the same mix as for
> the towerbase, ie sand:concrete ?

If you have more than 1 yard of concrete to pour, I strongly suggest  
you call a local ready-mix company. They will be able to bring a  
truck out to your lot and pour properly mixed concrete.

If you have less than 1 yard, you may be better off buying saks of  
pre-mixed concrete at your local home improvement store.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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