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Re: [TowerTalk] concrete

To: Artmouton <>
Subject: Re: [TowerTalk] concrete
From: David Gilbert <>
Date: Mon, 31 Dec 2007 10:40:14 -0700
List-post: <>

Even the manufacturers of various fibers (glass, nylon, polypropylene, 
steel, kevlar, spun carbon ... in approximate order of strength and 
cost) refer to them as "secondary reinforcement" and specifically state 
that they are not a substitute for rebar for structural strength.  They 
add localized strength and help to avoid small cracks, but will not hold 
a mass of concrete together like rebar will.  NEVER leave out a proper 
rebar skeleton ... concrete is fantastic in compression but totally 
unreliable in tension by itself.

By the way, the fibers you get from a typical concrete supplier are 
usually just some version of spun glass.  They are inexpensive and help 
to avoid small cracks as the concrete cures, but are almost worthless 
for longer term strength since the alkali in the concrete attacks the 
glass.  I've seen figures indicating that about 80% of the strength of 
simple glass fibers is gone after 30 days.  I went with glass fibers 
when I had the slab poured for this house because I laid down LOTS of 
rebar first and I was unable to talk the concrete supplier into using 
any other type of fiber anyway, but when I contracted to have stucco 
applied to the outside of the house I supplied my own nylon fibers to be 
added to each mixer batch.  I bought the fibers from, but 
they also sell steel fibers if anyone really wants to beef up their 
tower foundation ... or improve their UFER ground ;)

Dave   AB7E

Artmouton wrote:
> Or Rebar - or will both be best?
> Art K5FNQ
> (about ready to put base in for Rohn 55)
> ----- Original Message ----- 
> From: "Its from Onion" <>
> To: "towertalk" <>
> Sent: Sunday, December 30, 2007 7:48 PM
> Subject: [TowerTalk] concrete
>> Don't forget the use of fiber in the concrete mix.  
>> Lee
>> KE4VYN 
>> _______________________________________________

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