Mortar has a wide-spread range of applications. It is difficult to find a definition taking into account all these different uses. From the technical point of view mortar has to be defined by considering its constituent elements.

Definition of mortar: A mixtures of aggregates generally with a grain size of less than 4 mm (sometimes less than 8 mm, e. g. mortar for special decorative renders or floor screed mortar) and one or more binders and possibly additives and/or admixtures. Mortar with inorganic binders contains, in addition, water.

What is the origin of mortar?

The origin of mortar can be traced thousands of years. The oldest mortar was based on lime and sand. Since then building techniques have changed and new construction materials developed. Modern mortar is based on mineral aggregates like natural sand, and mineral binders like lime, cement or gypsum. Organic admixtures are added to improve special properties, e. g. workability, water retention or water proofing characteristics.

What are the functions of mortar?
The most important functions of mortar are:

· to bind materials together (e. g. masonry mortar and tile adhesive mortar)
· to provide a level or smooth finish (e. g. floor screed mortar, internal plastering)
· to protect against weathering (e. g. external rendering)
· to improve thermal insulation of walls (e. g. thermal insulation rendering mortar, lightweight masonry mortar)
· to repair and renovate constructions (e. g. concrete repair mortar, damproofing mortar, or renovation mortar)

What types of mortar are in use?
The currently most common types of mortar are:

· masonry mortar which is divided into general purpose mortar, lightweight mortar and thin layer mortar)
· rendering mortar which is used to protect buildings against weathering and to give them a decorative look. Thermal insulating renders are part of this group.
· plastering mortar to finish inside walls normally containing gypsum
· floor screed mortar cement based or based on calcium sulphate binders
· high-technology dry mortars (tile adhesive, concrete repair etc.)
· External Thermal Insulating Composite Systems (ETICS)