Towertalk
[Top] [All Lists]

Re: [TowerTalk] Using old concrete in new pour

To: David Gallatin <kc9eev@yahoo.com>
Subject: Re: [TowerTalk] Using old concrete in new pour
From: Al Kozakiewicz <akozak@hourglass.com>
Date: Wed, 22 Oct 2014 00:25:12 +0000
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
For every complaint I hear about how the stereotype of hams being cheap is 
unfair, there are 30 stories like this.

I've thrown chunks of old concrete and big stones into steps and slabs that are 
not structural in nature - they only need to support themselves and the 
occasional human walking across them.  Probably OK for a guyed tower where the 
base need only have some mass and a modest amount of compressive strength.

A tower base for a self-supporting tower is an engineered structure.  If you 
deviate from the plans, then the engineering is no longer valid and the 
specification of the resulting structure may be insufficient for the intended 
purpose.  Cement adhesion (is there a better term?) to the aggregate and other 
materials like old concrete tossed into the mix is not the same as the bond 
created in the cement itself on a particle level as concrete cures.  In that 
sense, "concrete is not concrete".

More worrying is the "soupy" adjective.  For a given concrete mix there is but 
one optimum amount of water to add.  Too much or too little and the concrete 
will be weaker than specifications.  You don't alter the flow characteristics 
of concrete by varying the amount of water added but with additives 
specifically designed for the purpose that do not affect the ultimate strength. 
 It strikes me that someone willing to save a bucks on concrete by reusing 
scrap knows nothing about plasticizers and would be giving doubly bad advice by 
suggesting you just add more water to the mix.

I would definitely ignore your friends suggestion.

Al
AB2ZY

________________________________________
From: TowerTalk <towertalk-bounces@contesting.com> on behalf of David Gallatin 
via TowerTalk <towertalk@contesting.com>
Sent: Tuesday, October 21, 2014 7:53 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Using old concrete in new pour

Hello everyone,
A ham friend today suggested using concrete from an old pad that's broken into 
small (maybe fist size or a bit smaller) pieces and using it in
a new pour, specifically for my new 30 foot aluminum tower. He said you make 
the new mix "a little soupy" and toss the old chunks in as you go, the idea 
being less new concrete is used (and paid for) and when it dries you can't tell 
a difference "concrete being concrete". He did not specify what kind of ratio 
of old to new is used but he does have two pads of his own he has done this 
with that hold 60' steel self supporting towers.
I have tried to research this and come up with nothing. I did find reference to 
concrete being recycled (crushed) into aggregate size and used as such in new 
pours but what he is talking about does not seem to be the same thing.

 Obviously I am a tad concerned about doing this. Has anyone heard of this 
technique before?

73,
David, AA9G

ex W5DCG and KC9EEV
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk

<Prev in Thread] Current Thread [Next in Thread>