The Best Cement & Ballast Mix for Concrete

Basic Ingredients

• Concrete has three basic ingredients, mixed together in different proportions. Portland cement is a mixture of hydraulic calcium silicate and calcium sulfate. The U.S. Department of Transportation lists eight types of cement that affect concrete in various ways including the hardness, high strength, water resistance and air entrapment. Another ingredient is the aggregate, or ballast. It is the filler around which the cement bonds. Sand is often used in general purpose concrete, with gravel and different kinds of crushed stone used when strong applications are needed.

Water

• Water is the final ingredient to make concrete. It is mixed with cement and the aggregate at different ratios to make anywhere from a thick paste to a fine liquid similar to a cake batter. The less water in the mixture, the stronger the concrete will be after it dries. It will also be less permeable to air and moisture. When mixing concrete for small home projects, the bag will list proper water ratios for different tasks.

Applications

• Different applications call for different kinds of concrete. Cold temperatures, moisture and chemical resistance, tensile strength, weight-bearing and low-cracking are all factors in the type of features that any one job may call for. Concrete poured during cold weather or concrete that is specially formulated to take longer to dry has further additional chemicals mixed in to provide the proper qualities. Fly ash from coal-burning plants can replace up to 30 percent of the cement for special projects.

Shrinkage

• Concrete shrinks as it dries. This is why sidewalks and highways have built-in cracks across them every few feet. As the material contracts, it cracks along the lines where the contractor wants it to, as opposed to somewhere in the middle. Decorative concrete, such as that found on decks, around pools and kitchen countertops, has a no-cracking formula that is used.