When making your own concrete it's important to use the correct concrete mixing ratios to produce a strong, durable concrete mix.
To make concrete there are four basic materials you need: Portland cement, sand, aggregate (stone), and water.
The ratio of aggregate to sand to cement is an important factor in determining the compressive strength of the concrete mixture.
One of the best concrete mix ratios is 1 part cement, 3 parts sand, and 3 parts aggregate, this will produce approximately a 3000 psi concrete mix.
The strength of this mix ratio is good for most concrete slabs, footings, steps, and foundation walls.
Mixing water with the cement, sand, and stone will form a paste that will bind the materials together until the mix hardens.
The strength of the concrete, after it cures, will be inversely proportional to the water/cement ratio.
Basically this means the more water you use to mix the concrete (very fluid) the weaker the concrete mix.
The less water you use to mix the concrete (somewhat dry but workable) the stronger the concrete mix.
Accurate concrete mixing ratios can be achieved by measuring the dry materials using buckets or some other kind of measuring device.
By measuring the cement, stone, and sand, you will have a consistent concrete mix throughout your entire project.
To produce a 3000 psi cubic yard of concrete (27 cubic feet) the concrete mixture ratio is:
This mixing ratio will give you a concrete mix that is strong, durable, and good for most concrete projects.
A cubic yard of concrete will fill an area 8 feet wide by 10 feet long by 4 inches thick, or 80 square feet @ 4 inches thick.
At 6 inches thick a cubic yard of concrete will fill an area 52 square feet and at 5 inches thick, it will fill an area that's 65 square feet.
To produce a cubic yard of 4000 psi concrete, you have to adjust the concrete mixing ratio to:
As you can see a little more cement and a little less sand is required to produce this stronger concrete mix that is great for driveways, pool decks, sidewalks, exterior patios, and commercial garages.
Knowing the weight of the materials and how much water to use should help you determine how much cement, sand, and stone to purchase to complete your project.
For estimating purposes, you can make about 1 cubic yard of concrete with 5 1/2 94-pound bags of cement, 17 cubic feet of sand, and 18 cubic feet of gravel. (It takes about forty 80-pound bags of prepackaged materials (like Quikrete) to make 1 cubic yard of concrete.)
Or... 1 cubic meter of concrete will require approximately 7.15 bags of Portland cement, .48 cubic meters of sand, and .51 cubic meters of gravel.
If you need less than 1 cubic yard of concrete (or if ready-mix is not available) you can mix your own on site either by hand, using the tools above, or by using an electric concrete mixer like the one in the link above.
To make smaller batches of concrete, use the same
proportions, but with smaller quantities, substituting buckets for
cubic feet. (For the mix proportions given previously, you'd use 1
bucket of cement, 3 buckets of sand, 3 buckets of stone, and 1/2 bucket
For any batch size, the most important thing is to keep the
proportions of the ingredients the same. You can double or triple the
batch size simply by doubling or tripling the number of buckets of each
ingredient you add to the mix.
The mix ratio of 1:2:3 consists of 1 Part cement, 2 Parts sand, and 3 Parts stone (plus some water) to make a concrete mix you can use for most any building project.
The way you measure the ratio could be in shovels, buckets, or wheel barrows. As long as you're consistent you'll get a good strong mix.
Generally, when the stone ratio is more than the sand, this concrete cures a little stronger than a 1:3:3 ratio. The difference is in the workability of the concrete. The sand tends to make the concrete a little more easier to work with. The less sand the rockier the mix is going to be.
These concrete mixture ratios are designed for the concrete to reach full strength at or around 28 days old.
Curing the concrete can be done by keeping it wet after the first day until the concrete is 7 days old.
Curing is an important step to take for the concrete to achieve full strength by 28 days.
Watch my video talking about what concrete mixing ratios it takes to achieve 3000 psi, 3500 psi, 4000 psi, and 4500 psi concrete.
I also break down the equivalent 20mpa, 25mpa, 30mpa, and 35mpa concrete mixing ratios.
Below you can use this concrete mix ratio calculator to determine how many cubic yards and bags of concrete mix it will take to do your project.
Make sure to use the proper dimensions (Feet and Inches, or Meters and centimeters) to get accurate results.
Once you know how many cubic yards or meters (or how many bags) it's going to take, you can figure out the weight and proportions of cement, sand, stone from there.
EXAMPLE: A project that takes TEN 80 lb bags of concrete mix, means you need 800 lbs of material.
A 1:3:3 mixing ratio calculates to 115 lbs of cement to 343 lbs of sand and 343 lbs of stone. (Rounded off)
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For more on concrete slabs see the information below:POURING A CONCRETE SLAB
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