What Are Concrete Mixing Ratios?
Concrete mixing ratios are the formula for calculating the correct amount of each ingredient used, including water, cement, sand and aggregate, to produce concrete with the properties desired. A basic concrete ratio is one part cement, two parts sand, and three parts gravel, slowly mixing in water until workable.
Water is the key ingredient, because the water-to-cement ratio is inversely proportional to the concrete's strength properties. Water must be added slowly to the mixture with a slump test performed to determine when the concrete reaches the correct, workable consistency. A slump test consists of filling an inverted Styrofoam cup that has the bottom removed with the mixture. When the cup is removed and the material settles, it should be one-half to three-quarters as tall as the cup for proper workability.