Mortar (masonry)
Workable paste that hardens to bind masonry units.
Mortar is a workable paste that hardens to bind building blocks such as stones, bricks, and concrete masonry units, filling and sealing irregular gaps, spreading weight evenly, and sometimes adding decorative colors or patterns. It has been used since ancient times, with early examples including mud and clay mortars in 10th millennium BC Jericho and 8th millennium BC Ganj Dareh, as well as gypsum and lime mortars in later structures.
- first_known_use
- 10th millennium BC (Jericho)
- common_binder_since_early_20th_century
- Portland cement
- ancient_binder_still_in_use
- Lime
- types_in_united_states
- M, S, N, O, K
Lore & Background
The first mortars were made of mud and clay, as demonstrated in the 10th millennium BC buildings of Jericho and the 8th millennium BC of Ganj Dareh. Gypsum mortar, also called plaster of Paris, was used in many ancient structures, requiring a lower firing temperature and setting faster than lime mortar, though it is less durable in damp conditions.
Reader's Guide
Mortar's significance lies in its role as the sacrificial element in masonry, being weaker and easier to repair than building blocks. The development of Portland cement mortar in the 19th century revolutionized construction, allowing faster building with less skilled labor, but its hardness and impermeability make it unsuitable for repairing historic lime mortar structures, which require flexibility and breathability. The loss of hydraulic mortar knowledge for nearly two millennia highlights the fragility of technical knowledge. Modern mortar types, standardized in the US as M, S, N, O, and K, offer varying strengths, and polymer cement mortars are used for concrete repair, though they may trap moisture in traditional walls.
Did You Know?
- The word 'mortar' comes from Old French 'mortier', meaning 'builder's mortar, plaster; bowl for mixing' (13th century).
- Gypsum mortar was used in ancient brick arch and vault construction because it sets much faster than lime mortar.
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