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


Hey smart math boy. Why don't you take yourself down to the local Home
Depot and look on the blue 80lb bags of concrete and then tell me what
it says. If it doesn't say 1 cu. ft. then come on back here and tell me
about it. Otherwise, why don't you shut up? I've got the bag right out
in the garage and I can read what it says. And I poured it and I know
how much space it filled. I don't care who Bob is or what he is pouring
but unless he is using the same bags I did then you can't say he is
right and I am wrong. Maybe we are both right. Either way, you are a
fool for thinking you know it all.