One bag concrete mixer ratio?

Butch(OH)

Well-known Member
This has been posted here before but has left me. I have a one bag mixer, that's a bag of cement, not sackcrete. How many shovels of sand and gravel to one bag? Seems to me it was 50? I have search and searched and all I can find is premixed sackcrete information.
 
One shovel cement, 2 shovels sand, 3 shovels gravel. Between me, my dad, and granddad, been doing that ratio for about 100 years. Never any reason to change. If you're going to do 50 shovels of anything to one shovel of cement, might as well save the cost of the cement and leave it out- result will be about the same.
 
I know about 3 2 1 and bla bka bla but was hoping someone would know the number of shovels of sand and gravel per bag of cement. Been posted here previously, I am writing it on the wall this time,LOL. Would save me some time in the morning figuring how many shovels are in a 94 lb bag of cement.
 
"Would save me some time in the morning figuring how many shovels are in a 94 lb bag of cement."

Well, you need to get the cement into the mixer somehow. A shovelful at a time will accomplish two things.
 
Guess I will have to shovel a bag in it and multiply times 5 to get sand and gravel. That I know how to do. We can buy the sand and gravel already mixed correctly at the pit, just add cement and water. For those that haven't been around one a one bag mixer is a big one.
 
(quoted from post at 18:20:49 05/25/18) Guess I will have to shovel a bag in it and multiply times 5 to get sand and gravel. That I know how to do. We can buy the sand and gravel already mixed correctly at the pit, just add cement and water. For those that haven't been around one a one bag mixer is a big one.
y 'edumacted' input says that it is 25 instead of 50 and you end up with 3 cubic feet of concrete. Keep us informed.
 
JMOR; getting 3 cubic feet of concrete from a 1 cubic foot bag of cement (94 lbs) would be a substantial waste of cement for general purpose concrete. Using the 1-2-3 mix that several others here have recommended provides a perfectly adequate general purpose concrete. It works out to about a 5-1/2 sack (of cement per yard of concrete) mix, which is about a half a sack richer than the mix you will get from a transit mix company unless you specify something else. Getting 3 cubic feet of concrete from a one cubic foot sack of cement would work out to be about a nine sack mix. You might need that rich a mix if you were casting containers for holding radioactive waste. I wouldn't know.

In figuring the volume of concrete you will get from the cement, sand, and aggregate, add the volume of each ingredient, then multiply the total by 0.85 (85%). The volume loss is because the sand fills in the spaces between the units of the aggregate and the cement fills in the spaces between the grains of sand. For practical purposes you can discount the volume of the water.

Stan
 
(quoted from post at 20:52:46 05/25/18) JMOR; getting 3 cubic feet of concrete from a 1 cubic foot bag of cement (94 lbs) would be a substantial waste of cement for general purpose concrete. Using the 1-2-3 mix that several others here have recommended provides a perfectly adequate general purpose concrete. It works out to about a 5-1/2 sack (of cement per yard of concrete) mix, which is about a half a sack richer than the mix you will get from a transit mix company unless you specify something else. Getting 3 cubic feet of concrete from a one cubic foot sack of cement would work out to be about a nine sack mix. You might need that rich a mix if you were casting containers for holding radioactive waste. I wouldn't know.

In figuring the volume of concrete you will get from the cement, sand, and aggregate, add the volume of each ingredient, then multiply the total by 0.85 (85%). The volume loss is because the sand fills in the spaces between the units of the aggregate and the cement fills in the spaces between the grains of sand. For practical purposes you can discount the volume of the water.

Stan
do not believe the 94# per cubic foot is a correct density. More like 196/cu ft. Factor off by about 2:1, I do believe.
 
Butch(oh); I find a shovel to be a convenient but inaccurate way to measure the components for mixing concrete. Cement stacks quite high on a shovel, sand less high (depending on the moisture content), and gravel hardly stacks at all. I welded 1" high back and sides on a regular spade and that helps some, but I like to know that my concrete is more consistent than that. You have a perfect situation for using some means of measuring that is more accurate and consistent than a shovel. Since your mixer holds a cubic foot of cement (which is bigger than any I've ever had the pleasure to work with), all you have to do is find an easy way to measure two feet of sand and three feet of aggregate. A five gallon bucket filled to the rim has a volume of 0.71 cubic feet. That means that three of them is 2 cubic feet, and four and a half of them is 3 cubic feet. Ten years ago I could lift a five gallon bucket full of sand or gravel and toss the contents into the mixer. Lately I've had to use half buckets.

My prediction is that you'll want to keep using the shovel to measure your components because it's easy and it's close enough.

Stan
 
Stan I know I get a lot of variation, especially when I get tired toward the end of the day. Yes a 1 bag mixer is a big one. We have it mounted to a quick tach plate and haul it between the gravel piles and the placement with our Case loader and it runs off the third valve. We have mixed a lot of concrete with it but it's been a while. Luckily it's not a critical job and we have a few batches to dump in the bottom while we get it right.
 
My dad and I mixed an awfull lot of concrete in a little old drum mixer. 123 or 321 what ever you like. 1 cement 2 sand and 3 gravel / aggregate. You want your sand washed and clean of clay. Same for the stone. Clay screws up everything and makes for very weak concrete. Adjust your water for slump. Don't add too much water cause it can mess up the chemistry of the curing process. I always mix a little on the stiff side. When you need to poke it with a stick that is thick enough. First time I saw the slip form machine doing curbs along a road. The stuff was way dryer than zero slump. Machine slowly moved along and the concrete just stood ther. About 15 feet down the work the curb was already turning white! Drying that quickly. Curbs are still there.
 
(quoted from post at 21:23:35 05/25/18) JMOR; No, a cubic foot of cement is 94 lbs. We don't have to argue about it, though. You're on the computer; Google it.

Stan
nteresting.
Google; Density (g/cm3) 3.15

(3.15X2.54X2.54X2.54X12X12X12)/454=196.47 lbs/cu ft

??????????
 
Google it.

Stan

From Google--
"In general, 1 yard of concrete weighs about 4050 pounds. 1 cubic yard of concrete equals 27 cubic feet. 4050 lbs divided by 27 cubic feet = 150 lbs. per cubic foot."
You're welcome. :D
BillL
 
Seems to me when we used ours,and it was a one bag mixer. I used to put in 45 shovels of cement gravel to one sack of cement powder. The concrete is still there 40 years later.
The cement gravel was a washed product with the sand and stone already mixed for the work. No need to figure the sand and stone separate.
 
JMOR; I'm totally stumped by this. I've been going over it for almost half an hour and I can't find the source of the problem. Your information is correct and your calculation is correct (at least I come up with the same figure), but it does not produce the right answer. Working backwards from the known values (1 cubic foot of cement = 94 lbs, 1 cubic foot of water = 62.45 lbs), it appears that the specific density of cement stated by Google of 3.15 has to be wrong. It should be 1.51. So far I haven't been able to come up with any other reasonable explanation. The most obvious answer would be that the term cement and the term concrete are used interchangeably, but the specific density of concrete does not work out to be 3.15 either. This will bother me until I find out what the problem is.

Stan
 
JMOR; I found the answer. The specific density of cement as packaged is 1.44 g/cc because it includes the air voids. The figure 3.15 g/cc is for cement that has been compressed until it contains no air voids. I wish I could say that I figured this out, but it's information I found. Persistence is good, too.

Stan
Specific gravity of cement
 
(quoted from post at 12:21:42 05/26/18) JMOR; I found the answer. The specific density of cement as packaged is 1.44 g/cc because it includes the air voids. The figure 3.15 g/cc is for cement that has been compressed until it contains no air voids. I wish I could say that I figured this out, but it's information I found. Persistence is good, too.

Stan
Specific gravity of cement
maybe if we fluff it up more, we can make a bag easier to handle at 75 pounds. :)
I wonder if the ready mix plants mix by volume or weight?
 
JMOR; It would have to be by weight, wouldn't it? There isn't the equivalent of a simple slump test which can be run at the job site to determine the cement content of fresh concrete; the test is complicated, time consuming, and requires scientific equipment such as centrifuges. If there's a way to cheat, there will always be some who will cheat. I imagine that the protection in the ready mix industry is that if you try to sell an inferior product, word will eventually get around. Then, you would not only lose future business but you would also be liable for all the provably bad concrete you'd sold in the past. Nobody can get away with cheating customers forever---with the possible exception of hedge fund managers.

Stan
 
The way I was taught by an 80 year old man when I was 18 was, A pail of water, three shovels of bank gravel, two shovels of screened sand, one shovel of cement and a big squirt of tobacco juice. Repeat the gravel, sand, cement and squirt of tobacco juice until mixer is full and add water until desired consistency is achieved. I stood on one side of the mixer and took care of the sand and gravel, he stood on the other and took care of the water, cement and squirt of tobacco juice.

Outside pads or walk ways I forgo the tobacco juice and used one and a half shovel of cement.
 
. Is that washed gravel with no sand in it ? We just use A grade road gravel. Ratio depends on the application . I would rather error on mixing it a little too strong instead of a little too weak.
 
the standard test to check the strength of concrete is to make test cylinders at the job site and break them at 28 days. Air content can also be checked at the job site-its done with a pressure cooker type device. Also the driver should have a batch mix ticket with all the weights of the ingredients
 
(quoted from post at 14:57:33 05/27/18) Weight

I've mixed a lot of concrete alone in a small mixer it held 2 shovels of cement and the bank run of gravel and water. I soon learned how much water it needed.
I would mix a batch, dump it, than put about 1/2 the water needed for the next batch in the mixed and lat it run, and then go and place the batch that I had just dumped. I learned that if I did not do that the mixer would build you one small layer after another, but putting in the water it rinsed the mixer drum down.
I understand that, that was not the proper proceeder for mixing concrete, but that is what worked for me.
That was almost 50 years ago.

Dusty
 
Dusty MI; In determining the proper way to do something, you have to give extra weight to what works and be more skeptical of the way that anyone else says is the right way if it doesn't work for you.

Stan
 

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