A contractor is delivering freshly mixed concrete to a friend’s house for repair work.
This friend is curious re: how much 1 cubic FOOT on liquid concrete weighs, allowing for variances in mixes.
I guessed somewhere in the 100-pound range. Any ideas?
Not a bad guess. 140 - 150 would be better.
whoops. I should note it will be poured from a cement mixer. The chart you link speaks of cement in a “slurry” form, giving a weight of 90 pounds per sq ft.
Would that be the correct term/weight?
From my concrete mixer driving days I was told that a cubic yard of concrete weighs just short of a ton.
Just divide a ton by 27 for an aproximate amswer.
That’s just a little more than water weighs–you put a lot of rocks in it, it’s going to weigh more
Solid rock runs 140 to 180 lbs. per cubic foot, depending on what type of rock. (Excluding the rare ones like pure gypsum, or Galena) While concrete will be variable, depending on what you use as an aggregate, it should be in the same range. So, 150 lbs. for a cubic foot seems entirely reasonable.
“It is when I struggle to be brief that I become obscure.” ~ Horace
No. Water is extremely dense and non compressible. If you substitute volume x of water with an equal volume of rock, the weight will likely go down, as rock is not as dense as water. Put a brick in a pan of water and watch how much water it absorbs via capillary action.
Rock is not as dense as water? Oh…so that explains all the floating rocks in my lake.
?? your average sex rock is two and a half times more dense than water
Well, maybe all the rocks around his place are pumice.
I took my son and some friends up to reservoir on the Los Angeles aqueduct near Bishop one time. One of them idly picked up a rock and threw it in the lake and the rock floated. They had a great time throwing the floating rocks in the water.
Architectural designer/engineer weighing in.
In my structural calculations I use 150 lbs per cubic foot for concrete.
Water weighs 8 pounds per gallon.
I think you have the decimal in the wrong place.
And there’s a factor of about 8 gallons per cubic foot
Water weighs 8.34 pounds per gallon and there are 7.48 gallons per cubic foot, therefore water weighs 62.4 pounds per cubic foot at normal temperatures (~60 - 80 degrees F).
An individual rock (or other mineral matter) has a density greater than that of water, however, it’s bulk density will be less because of void volume.
If the previously stated number of one ton per cubic yard then concrete would weight ~ 74.7 pounds per cubic foot which is too low.
I checked it out and here’s a link to site where the value is given as 135 - 142 pounds per cubic foot depending on the admixture and aggregates used.
Sounds about right. Fresh water weights 62.4 lb./ft[sup]3[/sup] and 2.5 times that is 156.
danceswithcats
If rock is not as dense as water, all rock would float.
Well it appears I’m wrong.
From Truck Mixer Driver"s Manual
May 1995
National Ready Mixed Concrete Association
The purpose of the unit weight is to find the weight of 1 cubic foot of concrete. Unit weight is measured in pounds of concrete per cubic foot,which is abberviated lb./cu.ft. Expect concrete to have a unit weight of 140 to 150 lb./cu.ft. Comcrete made with lightweight aggreates will have a unit weight of 115 to 125 lb./cu.ft.
I always thought that guy was blowing smoke most of the time anyway.
A what rock? 
any old fucking rock