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Re: [TowerTalk] Extending a concrete base?

To: "Paul Kelley N1BUG" <>,"towertalk reflector" <>
Subject: Re: [TowerTalk] Extending a concrete base?
From: "K8RI" <>
Date: Tue, 25 Sep 2007 14:58:26 -0400
List-post: <>

> Here's another (maybe stupid) question...
> I have a 25G tower with the bottom section partially embedded in
> concrete. Problem is the concrete was poured with the top only about
> an inch above ground. The base never moves but the surrounding earth
> frost heaves up slightly in winter. Spring snow melt and rain then
> deposits dirt and debris on top of the concrete where it then
> surrounds the tower legs. The tower is on sloped ground which
> promotes this action. I am tired of cleaning the dirt and debris off
> it every year and wonder what I can do to eliminate this situation.
> If I clean (wire brush?) the top of the existing concrete, build a
> wood form around it and simply pour another few inches of concrete
> on top, will I be helping or making matters worse? I am wondering if
> the new concrete will adhere to the old stuff adequately, or if
> water may tend to get in between old and new layers (where it would
> no doubt freeze and cause bigger problems).
It's quite likely the junction between new and old would foum a boundray 
layer where water would penetrate.

There have been a couple of good suggestions of etching as well as drilling 
and using rebar.

The typical etch is a dilute Muratic Acid which is then thouroughly washed 
away.  It comes with directions. Drilling and adding rebar would also help 
keep the new bonded to the old. However as you are only looking at a couple 
of inches with out the need for strength you *might* get away by simply 
doing the acid etch and wash prior to the small pour. OTOH if you have the 
room adding 6 inches of new concrete would give enough room to drill and pin 
with rebar and still have enough room to extend the concrete several inches 
above the rebar pins.

Good Luck,

Roger (K8RI)

> I have worked with concrete quit a bit, but have never poured new on
> top of old. Any advice would be appreciated.
> Thanks & 73,
> Paul N1BUG
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