Select good clean gravel or crushed stone. If the largest stones are not much larger than 1" in diameter and are well graded from fine to coarse, you have a fine start toward good concrete. A few larger stones will do no harm. The most important single ingredient that determines the quality of concrete is the sand. Sand must be clean and free from organic matter. This is a must. The grains should be sharp, not ocean sand that has been rolled until the grains are almost round.

Cement as you buy it from the dealers in the United States is almost certain to be good, unless it has been on hand so long that it has become lumpy, or has been wet and is partially hardened. If it is fine like flour and free from lumps, you can use it with confidence.

The best proportions for good concrete are to use one part cement, two and one-half parts sand, and three and one-half parts gravel. If you find natural river gravel and sand already mixed by nature, and it is clean, use it with one part cement to six parts sand and gravel.

Water for concrete work should be clean; the water that comes out of the faucet, suitable for domestic use, should be all right.

The mixing, with a concrete mixer or otherwise, and the placing has an effect on the quality of any concrete job equal to that of the quality of the ingredients.

Good concrete is not hard to make if you are willing to follow a few simple rules.

Select good clean gravel for the large aggregate. Ordinary river gravel is good if it is clean; if it is not clean, wash it with a hose, letting the water strike the gravel with considerable force. Arrange it so the water can run away from the rocks after they are washed. Avoid rocks that are active chemically, and avoid ores, quartz, sandstone, and mica-bearing rocks; just ordinary hard rocks are the best.

The quality of the sand has a much larger bearing on the quality of the concrete than the gravel. Sand is more liable to carry dirt in varied forms. Avoid sand that contains clay or organic matter. Sand should be well graded from fine to coarse and should contain some very fine particles, but these must not be clay.

The amount of water put into concrete is a matter of importance. The less water you use, if you still get a good workable mixture, the better. Concrete should not be so thin that it will run like gruel, and it should not be so stiff that it stands up dry.

It must not be so dry that it cannot be spaded into place, but it should not be so wet that it will run ten feet down the form when poured in at one place. Don't make it too soupy. When first put into a wheelbarrow it should not flatten out completely, but after you have wheeled it forty feet, it should be smooth on top. If it will smooth out under a pat of your hand, it is about right.

For the very best concrete do not use more than seven and one-half gallons of water to one sack of cement; a little less water is better, provided you can get a workable mixture. The strongest concrete has been made with about five gallons of water to the sack, but this requires mechanical vibrators and other means of compacting the concrete, not available to the average builder.

Concrete must be mixed thoroughly, and although it can be done by hand in emergencies, a concrete mixer will do the job a lot easier and generally much better. If you have to mix it by hand, mix it thoroughly about three times dry. Then add water and mix it through twice. It should then be in good condition.

Once you have the concrete you are ready to start work.