[TowerTalk] Concrete testing

[k2qmf at juno.com]

Yeah!!   Talk about overkill........

 
On Thu, 2 Sep 2010 10:34:23 -0500 Michael Goins <wmgoins at gmail.com>
writes:
> Good Lord. Whatever happened top Joe Average Ham and just pouring 
> concrete
> for a base? I can see all this if you have an gigantic hundreds of 
> feet high
> superstation, but the average guy doesn't need to have his concrete
> analyzed.
> 
> You dig the hole the tower manufactuer specifies and you use the 
> rebar/cage
> they say. You guy correctly if it is guyed tower. You add concrete 
> and make
> sure there aren't voids. 99.999% of us need nothing more than that.
> 
> Mike, k5wmg
> Pipe Creek, Texas
> Green cars, slow boats, big dogs, old trucks, little radios, and 
> summers off
> to write
> 
> 
> 
> 
> 
> 
> On Thu, Sep 2, 2010 at 8:22 AM, Jim Thomson <jim.thom at telus.net> 
> wrote:
> 
> > Thank you for the suggestions.
> >
> > I called Advanced Testing in my area and got some information.  
> First, I
> > checked the trustworthiness of the concrete company.
> > That checked out.  The technical person I spoke with had a lot 
> experience
> > with concrete testing and curing.  A 4" slump and
> > no more for this job.
> >
> > ###  When those  4 x cylinders are poured, [all at the same time]  
> the 1st
> > cylinder is put in the hydraulic squasher after 7 days.
> > Cyl #2 gets tested after 14 days.   Cyl #3  after 21 days....and  
> #4  after
> >  28  days.   I never have it done...unless a PE says to do it.
> > If  more than one cement truck is involved.... then you have to  
> obtain 4 x
> > samples  from each truck !   Everything has to be labeled.
> >
> >
> >
> >
> >  However, due to the very warm temperatures in the north east, I 
> should
> > cover it with plastic to keep
> > the moisture from evaporating off the top.
> >
> > ## whoa!    Make damn sure u use a 15'  long vibrator  with at 
> least a 1.5"
> >  head on it..and don't over
> > vibrate the concrete.   They are cheap to rent.   You can also get 
> em with
> > a 2"  diam head.  Both heads
> > are aprx 12"  long.   Stuff the vibrator in, and turn it on... and 
> it will
> > flatten a mound of cement in 1 sec flat.
> > You can also drag it across..and make concrete  flow into the 
> corners, or
> > where  you want it.  Another trick
> > is to vibrate the cage itself..or the form.   You need one person 
> to
> > operate the vibrator..and a 2nd
> > person to turn the switch on/off.
> >
> >
> >
> > ##    A lot of times the cement truck operator will ask you if you 
> want it
> >  wetted down a bit..
> > so it pours easier.    If you add water.. you will weaken the mix. 
>   If
> > there is any standing water in the
> > bottom of the hole..it will weaken the mix as well... and  has to 
> be pumped
> > out.
> >
> > ##  some folks will lightly spray the sides of the hole with 
> water... to
> >  slow down any evaporation on the 5 x sides.
> > Some will line the 4 x vert sides with  4-6 mil  plastic 
> sheeting..to do
> > the same thing.
> >
> > ## as far as the top goes... AFTER troweling is done... I cover 
> all exposed
> > concrete  with old   [clean] bed sheets.
> > Then let it set up for an hr.    Then LIGHTLY mist it with the 
> water
> > sprayer.   Then do it again an hr later... with progressively
> > more water.    You will find that the top of the concrete  block 
> will  suck
> > the water  right up.... and then the chem
> > reaction starts up.    A few mins later... you can feel the heat 
> pouring
> > out the top of the wet sheets !   I repeat the
> > same process  [esp on a hot day]   for  abt 6-7 days in a row.   
> If the
> > concrete is poured  at 10 AM... it's  still getting water
> > on it at midnight..and quickly gets sucked up.    It's dry as a 
> bone  very
> > quickly..depending  on  outside temp.
> > You won't end up with any hair line cracks either..not with the 
> top closed
> > off..with a layer of rebar 5" below it.
> >
> > ##  I just pumped in 17  x yards  of  5075 psi   [35 mpa]  
> concrete on Aug
> >  16th.....it's still curing.  I had to morph
> > the new  UST  HDX-689 base into the adjacent old  Trylon base.  
> [which is
> > flared on all 4 x sides]   One side of the
> > old base  forms one  side of the new base.  Old base is  5.5' 
> square x  6'
> > deep.   New base is 7' x 6' 3"   x 9' deep.
> > 1025 lbs  of rebar went into the new base.  1"  for the 24 x 
> verticals. [
> > UST uses 16 vertical's]... and  5/8"  for the
> > 14 x horizontal tires. Ties are spaced every 6"  for the 1st 10 x 
> ties..
> > then every  1'  for the last 4 x ties.
> > Both vert +  Horz are  60 ksi weldable material.   The  12 x 
> anchor rods
> > are  5'  long  with  6"  threads on each end.
> > 105 ksi  rods used. They are in 3 x grps of  4 each... on 5''  C 
> to C.
> > Instead of the usual flatwashers on the bottoms of the
> > rods... we used a 9" x 9"  x  1/2"  thick steel plate...with  4 x 
> holes
> > punched.     That alone increases the
> > pull out capacity through the roof.
> >
> > ## Local PE and city hall  wanted the cage closed off on the top 
> too..with
> > a  8x6 grid of bars....
> >  and also a 2nd parallel  grid of bars down  4.5'.   The reason 
> was to
> > surround the 12 x anchor
> > rods on all SIX sides.   UST spec's  a   4.5'  square  cage.     
> We used a
> > 5.5'  square cage.  UST sez to use
> > short  27" long anchor bolts  [ 55 ksi]..we used   60" long rods  
> [105 ksi]
> >    IMO... 27" long anchor bolts
> > seems strange.  You have 6" of threaded  rod above the concrete  
> [which is
> > already 6"  above the lawn]
> > That only would leave  15"  of anchor bolt  below lawn level !    
> I can't
> > see digging a 9' deep  hole...
> > and having 15" rods embedded.    Local PE wanted the depth of the 
> rods to
> > be at least  1/2 the depth of
> > the hole.  It was decided that since the  105 ksi rods are  only 
> 13%  more
> > $$... but are 91%  stronger, to
> > use the stronger stuff.    So in went more re-bar, etc.   Since a 
> line pump
> > was used this time... the mix
> > used 3/8"  aggregate [ so the 3" line pump won't clog] .  Took 55 
> mins to
> > pump in  17 yards..with the
> > load split between 2 x trucks.    I hope city hall is happy.  17 
> yards in
> > new base morphed into  8 yards
> > of old  base =   50.625 tons.   I'm sure a hellfire missile would 
> bounce
> > off it.    I have pix of all this.
> >
> > Sri for the diatribe.
> >
> > later... Jim   VE7RF
> >
> >
> >
> >
> >
> > I will keep the group posted and post more pictures.
> >
> > Thanks.
> >
> > Anthony
> > _______________________________________________
> >
> >
> >
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> >
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