The first mortars were made of mud and clay. Because of a lack of stone and an abundance of clay, Babylonian constructions were of baked brick, using lime or pitch for mortar. According to Roman Ghirshman, the first evidence of humans using a form of mortar was at the Mehrgarh of Baluchistan in the Indus Valley, Pakistan, built of sun-dried bricks in 6500 BCE.[1] The ancient sites of Harappan civilization of third millennium BCE are built with kiln-fired bricks and a gypsum mortar. Gypsum mortar, also called plaster of Paris, was used in the construction of the Egyptian pyramids and many other ancient structures. It is made from gypsum, which requires a lower firing temperature. It is therefore easier to make than lime mortar and sets up much faster, which may be a reason it was used as the typical mortar in ancient, brick arch and vault construction. Gypsum mortar is not as durable as other mortars in damp conditions.[2]

In early Egyptian pyramids, which were constructed during the Old Kingdom (~2600–2500 BCE), the limestone blocks were bound by a mortar of mud and clay, or clay and sand.[3] In later Egyptian pyramids, the mortar was made of gypsum, or lime.[4] Gypsum mortar was essentially a mixture of plaster and sand and was quite soft.

In the Indian subcontinent, multiple cement types have been observed in the sites of the Indus Valley Civilization, such as the Mohenjo-daro city-settlement that dates to earlier than 2600 BCE. 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.” Bitumen mortar was also used at a lower-frequency, including in the Great Bath at Mohenjo-daro

calcium carbonate;a high percentage of lime
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