Mortar (masonry)

Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colours or patterns to masonry walls.

[2] According to Roman Ghirshman, the first evidence of humans using a form of mortar was at the Mehrgarh of Baluchistan in what is today Pakistan, built of sun-dried bricks in 6500 BC.

Gypsum cement that was "light grey and contained sand, clay, traces of calcium carbonate, and a high percentage of lime" was used in the construction of wells, drains, and on the exteriors of "important looking buildings."

The excavation of the underground aqueduct of Megara revealed that a reservoir was coated with a pozzolanic mortar 12 mm thick.

[8] Even later, the Romans used a mortar without pozzolana using crushed terra cotta, introducing aluminum oxide and silicon dioxide into the mix.

[11][12] It is not understood how the art of making hydraulic mortar and cement, which was perfected and in such widespread use by both the Greeks and Romans, was then lost for almost two millennia.

Since cured lime mortar can be degraded by contact with water, many structures suffered over the centuries from wind-blown rain.

It was invented in 1794 by Joseph Aspdin and patented on 18 December 1824, largely as a result of efforts to develop stronger mortars.

[13][14] In the United States and other countries, five standard types of mortar (available as dry pre-mixed products) are generally used for both new construction and repair.

Polymer mortar has low permeability that may be detrimental to moisture accumulation when used to repair a traditional brick, block or stone wall.

Alternatively, a pozzolanic material such as calcined clay or brick dust may be added to the mortar mix.

Addition of a pozzolanic material will make the mortar set reasonably quickly by reaction with the water.

In old buildings with walls that shift over time, cracks can be found which allow rain water into the structure.

It was originally discovered and dug at Pozzuoli, nearby Mount Vesuvius in Italy, and was subsequently mined at other sites, too.

Pozzolana has since become a generic term for any siliceous and/or aluminous additive to slaked lime to create hydraulic cement.

[22][23][24][25] Radiocarbon dating of mortar began as early as the 1960s, soon after the method was established (Delibrias and Labeyrie 1964; Stuiver and Smith 1965; Folk and Valastro 1976).