When making 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.
A concrete mixture ratio of 1 part cement, 3 parts sand, and 3 parts aggregate will produce a concrete mix of approximately 3000 psi.
Mixing water with the cement, sand, and stone will form a paste that will bind the materials together until the mix hardens. The strength properties of the concrete are 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 mixing ratios you will have a consistent concrete mix throughout your entire project.
Mixing ratio to make 1 yard of concrete
To produce a 3000 psi cubic yard of concrete (27 cubic feet) the concrete mixture ratio is:
1. 517 pounds of cement
2. 1560 pounds of sand
3. 1600 pounds of stone
4. 32 – 34 gallons of water
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:
1. 611 pounds of cement
2. 1450 pounds of sand
3. 1600 pounds of stone
4. 33- 35 gallons of water
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, pooldecks, 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 to make 1 cubic yard of concrete.)
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