Mortar is a workable paste which dries to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as used between mud bricks. The word “mortar” comes from Latin mortarium meaning crushed.
Cement mortar becomes hard when it cures, resulting in a rigid aggregate structure; however, the mortar functions as a weaker component than the building blocks and serves as the sacrificial element in the masonry, because mortar is easier and less expensive to repair than the building blocks. Bricklayers typically make mortars using a mixture of sand, a binder, and water. The most common binder since the early 20th century is Portland cement, but the ancient binder lime mortar is still used in some new construction. Lime and gypsum in the form of plaster of Paris are used particularly in the repair and repointing of buildings and structures because it is important[why?] that the repair materials are similar to the original materials. The type and ratio of the repair mortar is determined[by whom?] through a mortar analysis. Several types of cement mortars and additives exist.