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@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
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|