First, it is important to understand that cement is just one ingredient of concrete; these two terms are not synonymous. Concrete is the mixture of water, some type of aggregate — such as crushed rocks or sand — and cement, which acts as a binder to hold all the materials together once hardened. Evidence suggests that the ancient Romans were the first to use the concrete mixture in construction, and structures like the Pantheon stand as proof of the success of their invention.
Mortar, in its most general and basic form, is referred to as Portland, or Type One, cement and is created by burning limestone with other materials at 2,642°F (1,450°C). The result is then ground to produce a fine powder, which becomes one of the components of concrete. Altering the amounts of the other materials in the burnt mixture yields several different types of Portland cement, however, each type having unique properties and strengths. The type of mortar used in building a structure should be chosen based on the structure’s purpose and environment.
Because structures have various chemical and physical requirements, eight different types are manufactured. These types are simply referred to as Type One, Type Two, Type Three, Type Four, Type Five, and Type One-A, Type Two-A, and Type Three-A. Types One through Five are distinctly different, while Types One-A, Two-A, and Three-A are modified versions of their counterparts.
Type One is suitable for most basic construction uses. Type Two is best for structures built in hot environments, or in soil or water high in sulfate. For projects requiring strength at an early stage, Type Three is ideal because it provides more strength within one week than the other types. Type Four is useful in limiting heat caused by hydration and is therefore used in massive concrete undertakings, such as dams. When soil or water is high in chemicals, Type Five should be used because it is manufactured to resist chemical erosion.
The final three types of mortar are known as the air-entrained cements, because they have microscopic air bubbles added to their mixtures to increase the durability of the concrete. Air-entrained cements are especially useful in environments that have repetitive freezes. Types One-A, Two-A, and Three-A are similar in properties to Types One, Two, and Three; the air-entrained ones simply contain air bubbles.
There are also variations on these eight types that affect the color of the resulting concrete. For instance, white can be made by leaving out raw materials such as iron and manganese, which give concrete its traditional gray coloring.