Mixing Concrete

Blue Rock Station,
1190 Virginia Ridge Rd.
Philo Ohio 43771 USA
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Mixing Concrete

We all know what it is… but what is it?

Concrete is everywhere (or so it seems). The production of cement (that part of concrete that makes it what it is) takes a pretty big toll on the environment, so best to use it sparingly. But nearly every modern building project needs a bit, so let’s remind ourselves how to make it.

Basically, concrete is what you get when you mix Portland cement (not a brand name), sand (a fine aggregate), gravel (a course aggregate) and a bit of water. Stir, let it dry and, voila, concrete.

Easy as 1-2-3

The trick to making concrete is to remember how much of each item you add to the mix. It is recommended that, for general-purpose jobs (the type you are likely to be tackling if you are reading this to figure out how to do it), the ratio should be 1 part Portland cement, 2 parts sand (fine aggregate) and 3 parts gravel (course aggregate).

Just add water

Whether you are using a cement mixer or mixing the batch by hand, we recommend that you add water using a small bucket – rather than a hose. Our experience is that you just can’t control the amount properly with a hose and end up with too much water. It doesn’t take a lot, so be patient and add just a little at a time.

Clean water (if you can drink it, you can use it to mix concrete) is best. Dirt, salt, oil and whatnot will make your mix less than it should be.

Add just enough water to get a good thick oatmeal-like glob. Too much water and your concrete will be weakened. Too little and it is hard to work.

Three ways to get your concrete mix

1. Mix it yourself, either using a handy cement mixer or by hand. If using a mixer, you will know the mix is ready when it falls away from the blades and the back of the mixer. When mixing by hand, you will know it is ready with the mix is a uniform color and consistency and you are thoroughly exhausted.

2. Buy pre-mixed bags. For small projects (like setting a post) it is too much trouble and mess to mix it all yourself. You can buy bags of premixed blends. Just add water and away you go.

3. Call in the professionals. If you have a really large project, it just makes sense to have it delivered. If you are going to do this…

a. First, can the big, really heavy vehicle get to where you want the cement? Take this into account as nothing spoils an afternoon like having to push several hundred wheelbarrows full of cement mix.

b. Forms and wire mess should be in place and ready to go. When the guy with the truck shows up, he is not going to want to wait around while you get the final details in order.

c. Have a place to dump the excess cement mix. Usually they will show up with just a bit extra, and they will want to empty the truck before they go. Be prepared for this and have a place ready to take any excess.

d. Estimate the proper amount for the job. Ready-mix cement is purchased in cubic yards – a measurement that is meaningless to most normal human beings. So here is a quick guide to estimating cubic yards:

Cubic Yards

1. Measure the length and width of the project in feet. Then measure the thickness of the concrete you need. If the thickness is, for example, 3 inches then convert the inches to fractions of a foot, which in this case will be 1/4 ft.

2. Multiply the length, width, and thickness together and then divide it by 27 (27 is the number of cubic feet in a cubic yard). Now you will have the number of cubic yards of concrete you'll need. For example: 12' (length) x 10' (width) x 1/4 ft. (3 in. thickness) divided by 27 = about 1.1 cubic yards.

3. Then add on a little more concrete than you need to the cubic yards. This is better than not having enough. Add on 15 percent more for walls and footings and 20 percent for slabs. In this example you would then order about 1.3 cubic yards.

- Ideas in this brochure “recycled” from www.kent.net