[Antennas] RE:Concrete To Use For Your Tower

Mon, 9 Sep 2002 08:42:01 -0700

Perhaps you might consider following the tower manufacturer's
instructions for both the concrete and the rebar (see the message
below).  The only tower specs I have at hand are from Rohn and U.S.
Tower, but they are quite explicit and I am sure other manufacturers
also describe the requirements, as determined by their PEs.  Often this
information is required when obtaining building permits for towers.

73,
Bob, N7XY

On Mon, Sep 09, 2002 at 07:41:54AM -0400, Dave - N1PC wrote:
> I have put up several towers over the years with at least a yard of
> concrete at the base and have never used rebar.  Ignorance I guess.
> 
> I'm gonna be putting up another one in the next year or so and this one
> will need to last a long time!!!  
> 
> Let's say I have a 3' x 3' x 3' hole.  How should I orient the rebar.
> Fill me in on the whole process guys.....
> 
> Thanks and 73,
> 
> Dave, N1PC
> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Wendell Wyly W5FL
> Sent: Sunday, September 08, 2002 9:21 PM
> To: Chris BONDE; Karl Kanalz
> Cc: [email protected]
> Subject: RE: [Antennas] RE:Concrete To Use For Your Tower
> 
> 
> For non structural applications, fiberglass should do fine.  4 inch
> slabs, small retaining walls, lightly loaded concrete tanks, etc.  Where
> there will be thousands of pounds of tension, good old 5/8 and larger
> rebar will remain king.  Concrete has very good compressive strength -
> hence the 3000 - 5000 psi rating.  In tension it breaks very easily.
> High strength concrete is never made from a pea gravel (sack-crete) mix,
> rather using 1 to 1 1/2 inch rock in the mix to add tensile strength,
> when combined with rebar in the areas of the concrete that will be put
> under tension, it is a very strong structural member.  The rebar has
> ridges that prevent it pulling out and does not depend on a good bond
> with the concrete mix, although if you have ever taken a sledge and
> broken it off, it bonds better than you think.
> 
> Don't wait to put up your tower for a replacement to re-bar.
> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Chris BONDE
> Sent: Sunday, September 08, 2002 7:03 PM
> To: Karl Kanalz
> Cc: [email protected]
> Subject: RE: [Antennas] RE:Concrete To Use For Your Tower
> 
> 
> At 01:12 PM 2002-09-08 -0500, you wrote:
> >Yes there are, Dave!  Again, the user must refer to the manufacturer's 
> >recommendations for the size of re-bar to be used and the recommended 
> >"pattern" of how the re-bar(s) are connected together (usually in a 
> >sort of "cage" shape).
> >
> >Karl K -  W8TIF
> >McKinney, Texas
> Has anyone studied the use of concrete with fibre glass ans reinforcing?
> There are a few reports out that the concrete is stronger!  The rebar is
> usually oxidized before the concrete is pured hence a poor bond sithe
> the concrete.  The fibre glass (I think that is the strings that is
> mixed with the concrete) adheres and the mass is much stronger as it
> becomes a solid mass rather than a mass interupted with poor iron.
> 
> Has anyone anything thereon?
> 
> Chris opr Ve7HCB
> 