Concrete Formula
- Pure cement powder is the masonry base of concrete. You can find it at most home improvement stores or at a construction supply warehouse. It works similarly to paste, holding the other additives together. If you were making a cake, cement would be the plain batter. Concrete requires one part of cement powder.
- Fine aggregate helps give concrete its texture, hold its consistency and remain workable. An example of a fine aggregate is clean sand. Fine aggregates are small enough to pass through a number four sieve, but are retained by a number 200 sieve. In the cake analogy, fine aggregate would be the baking powder. Concrete requires two parts fine aggregate.
- Coarse aggregates add strength to and maneuverability to concrete and helps it to fill forms and other spaces. Coarse aggregates include gravel and pebbles. Aggregates defined as coarse will not pass through a number four sieve, but are still small enough not to be retained by a number three screen. Coarse aggregate is like the nuts or chocolate chips in the cake. Three parts coarse aggregate are used when making concrete.
- Water is what turns dry concrete mix into usable concrete. The amount of water that you will add to your dry concrete mix depends on how much concrete you are making and what you are using it for. Standard pourable concrete has a uniform texture, and the consistency is similar to slightly loosened toothpaste or peanut butter.
- Air is a key ingredient in concrete, and the mix must therefore be sufficiently aerated before use. If you are using a concrete mixer, you can allow the concrete to spin in the drum on low speed for 15 to 20 minutes in order to incorporate enough air. If you are mixing the concrete by hand in a container, use a large shovel to fold the concrete repeatedly for 20 to 30 minutes. Folding is a motion that is also used in making a cake, and requires picking up a portion of the mixture, turning it over, and dropping it over a bit from its initial position.
