Reginald P. Smithers III wrote:
basskisser wrote:
Reginald P. Smithers III wrote:
basskisser wrote:
Reginald P. Smithers III wrote:
basskisser wrote:
Reginald P. Smithers III wrote:
basskisser wrote:
Reginald P. Smithers III wrote:
Reginald P. Smithers III wrote:

Show me that concrete mix design that has 2500# of Portland cement in
it, and weighs better than two tons, and we'll go from there.
ps When I said Portland Cement weighed approx. 2500 lbs, I was referring
to Portland Cement, I never said or hinted that one would put 2500 lbs
of Portland Cement into a yard of concrete mix.

Have you looked over your concrete mixes to see that it is very common
for a yard of concrete to weigh approx. 4000 lbs?

One would not expect a PE to make sure a mistake.
No, it is not. Need proof? And if I show proof, will you admit your
mistakes? And where is that 2500 pounds of Portland cement per yard
used? Please show some criteria for your two tons, and your 2500 pounds
of Portland.

I tried to be helpful and show you many links showing you the exact
weight of concrete, and the exact weight of Portland Cement, you prefer
to ignore them. I didn't want you to continue with your silliness, but
I should have known better. The question wasn't "is all concrete 4000
lbs per year", because there are light weight concrete mixes that weigh
less, but as Bill said, concrete can and does weigh approx. 4000 lbs.
The fact that you fail to see this, does understand why you are not
employed.
No, you are wrong. Bill actually said that concrete weighs 5000#.
Please show what facts you have that I am not employed, first. Now,
where WERE those links that you shown that states that there is 2500#
of Portland cement in a yard of concrete? You DO know, seeing how you
are acting the expert here, that in reality, there's somewhere around 5
bags @ 94 pounds in a typical 3,000 psi mix, for a total of 470# don't
you? So, I'd really, really like to see this mix design that uses
2500#, because with a water/cement ratio of .53 maximum, you'd have
approx. 1,325 pounds of water. But you know this, right? Now, here's
the thing. a yard of concrete is an AREA. This 2500# of cement takes
approx. 12.72 cubic feet of area. The water that we need per ACI 307
would take an area of approx. 20.64 cubic feet, for a total of 33.36
cubic feet. You're now at more than a yard before you add in the
largest volumes, which are the coarse and fine aggregates, with proper
gradation of course. So, for an F'c of 3000 psi, the aggregate total is
going to be close to approx. 10 or 12 times the amount of concrete. So
now you have a "yard" of concrete that is 400 or so cubic feet! So, I'm
really confused. Please show me where you are correct, and I am wrong.
Now remember something about that 4,000 pounds you are referring to.
There is a factor of safety involved for that number. A cubic foot of
normal weight concrete doesn't weigh 150 pounds, although that number
is thrown around alot. The actual weight of normal weight concrete is
around 125 pounds per cubic foot, or 3375 a yard. If you'll look at ACI
guidelines you'll even see that there criteria uses 125# per cubic foot
dead load for elevated slabs! And even THAT has a factor of safety.

Do you understand English?
Yes, I do. So, show me how you can get 2500# of portland cement into a
yard of concrete using the criteria set forth by A.C.I. 307, A.C.I.
301, and A.C.I. 318. Do you also want me to post some design mixes here
showing that I'm right and you are wrong about the weight of concrete?
Also, do you want to show me how you get 150# per cubic foot, when,
following guidlines by ANY applicable code in the U.S., and ACI, and
even Factory Mutual, you only need to design a structure to resist 125#
per cubic foot?

Please go back and reread this thread before you respond. You might be
able to understand the words if you read them a 2nd time.

I want YOU to tell me, in YOUR WORDS, how applicable codes, all ACI
publications that deal in the subject, Factory Mutual, as well as the
Steel Deck Institute, etc. all allow you to design elevated structures
that will resist the forces of concrete floors at #125 per cubic foot,
which equates to #3375 per yard. All of these use a factor of safety,
also. SO, how is it safe to do that, if concrete weighs #150 per cubic
foot, as you say? Tell me.


If you go back through the thread you will see that concrete's weight
can vary based upon the aggregate used. I am surprised that a PE does
not understand that. Now if you go back to the beginning of this thread
and read it very slowly you will have all of your questions answered.
They are all answered already.

I never ever said that a yard of concrete's weight doesn't vary. BUT,
you've stated that it's at 2 tons, that is wrong. I want YOU to tell me
how someone can, by all applicable codes, case studies, etc. be able to
design for concrete structures at 125# per cubic foot, when you say
that concrete weighs 150#. Also post any binding data that you have
that concrete weighs 150# pcf.