RicodJour wrote:

User Example wrote:

Robert Allison wrote:

User Example wrote:

I have an 80lb bag of premix concrete in my garage that says 1 cu. ft.
on it. And based on use, I'd say it is right.


And you would be wrong. I have done about 600 replacements of balcony
decks on apartment complexes (2" of concrete on a wooden substrate, each
about 6'x8'). The first ones that we did, I measured the cubic feet
needed for the deck and bought the appropriate amount of bags (marked 1
cubic foot). On the first one we were 12 bags short. I recalculated
and it came out the same.

I returned to my concrete supplier (instead of home depot) and bought
identical weight bags of concrete (80 pound bags). These, however, were
marked .60 cubic feet. I did the calculations again. The next deck had
1/2 bag leftover.

Now I use the .60 measurement and it comes out pretty close every time,
even when I buy the stuff at home depot that is marked 1 cubic foot.


No. I would be right. I made a 35" x 16" x 6" form and it took less
than two bags. Do the math. Not sure what you are using but you don't
get as much per bag.


Let's see, you did one little form, and Bob did 600 much larger
placements. So your one test outweighs his 600? Yeah, right.

The manufacturers' literature (all of them) indicate .6 CF.

They also state to add 6-9 pints (2.8-4.3 liters) of water. 1 liter =
2.2 pounds, use the high number weight of water = 4.3 x 2.2 = ~9.5
pounds

Your version has concrete weighing 90 pounds (80 pound bag, plus ten
pounds of water - and some of that water evaporates). That's some damn
light concrete! Real world concrete, as opposed to imaginary, weighs
in at ~150 PCF. Even lightweight concrete using flyash and other
much-lighter-than-usual aggregate weighs in over 100 PCF.

Let's check Bob's version:
2 bags @ 80# = 160#
2 x 4.3L water = 19#
totals to 180#
manufacturer's lit, .6 CF/bag x 2 = 1.2 CF
180#/1.2 CF = 150#/CF

His numbers check, yours don't.
Do the math.

R


Exactly.

I hate bags of concrete. I love trucks full of concrete with
a pump truck.

We just poured a new slab today with a 36 meter pump truck and
16 trucks of concrete. Easier than one of those damn 6 x 8
decks. At one point we were doing 12 of those decks per day.
That took pallets and pallets of concrete mix, 4 halfyard
mixers, and a crew of 24. We placed that 128 yards of
concrete with 8 guys (not counting the truck drivers or pump
operators).

--
Robert Allison
Rimshot, Inc.
Georgetown, TX