[TowerTalk] Tower base pouring

[Gene Smar]

Doug:

     Yes, it does matter.  If you interrupt the pour, you'll need to take
special measures to ensure an intergral attachment of the two pours.  I
believe there is a liquid material that you'd have to apply to the first
concrete surface to seal the space between the two layers, but that doesn't
give you the mechanical strength that a single, monolithic pour would.

     I ran into the same thing when I poured my tower's foundation.  I
underestimated the amount of concrete I would need.  I have since learned
that when I vibrated the concrete (see below), I probably compacted the mix
more than had I not vibrated it.  Also, I believe I simply rounded my form's
dimensions down (wishful thinking) and ordered too little mix.

     When the first truckload was dumped into the hole, the mix came right
up to ground level - but the wooden cap that I framed the hole with was
empty.  The truck driver had to radio in for another yard and a half of mix.
The day was pretty hot and the original mix started to set up.  But we kept
it wet until the second truck arrived a half-hour later with the extra yard
and a half.

     Vibrating:  when you pour conrete into a form, it has a chance to
entrap air bubbles.  These bubbles tend to weaken the ultimate strength of
the mix.  So you can cause the air bubbles to escape by mechanically
vibrating the mix as it sits in the excavation.  I rented a
eletrically-powered concrete vibrator.  That's nothing more than a rubber
hose-like thing with a vibrating steel end that you sink into the mix as it
sits in the hole.  This will cause the mix to migrate into the nooks and
crannies of the hole, and cause the air to excape.  But don't vibrate too
much; the aggregates (rocks) will begin to settle out and you end up with a
weaker mix.

BOTTOM LINE:  Schedule your conrete delivery so you can pour it all at one
time.

73 de
Gene Smar  AD3F


----- Original Message ----- 
From: <douglas.snowden at med.va.gov>
To: <towertalk at contesting.com>
Sent: Thursday, July 22, 2004 12:10 PM
Subject: [TowerTalk] Tower base pouring


> Someone mentioned that they poured and underestimated how much concrete
they
> needed.
> Does it matter if you pour 3/4 of it and then come back in a few days or a
> week and finish it
> up?
>
>
>
> Doug, N4IJ
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk