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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