Sarooj is a traditional water-resistant mortar used in Iranian architecture,[1][2] used in the construction of bridges,[3] and yakhchal.[4] It is made of clay and limestone mixed in a six-to-four ratio to make a stiff mix, and kneaded for three days [citation needed]. A portion of furnace slags from baths is combined with cattail (Typha) fibers, egg, and straw, and fixed, then beaten with a wooden stick for even mixing. Egg whites can be used as a water reducer as needed.
Mosaddad et al report the use of a mixture consisting of lime, sand and ash in the construction of an 1800 year-old Sasanian bridge-dam on the Karoon river south of Shooshtar.[3] The Sheikh's biogas bath-house in Isphahan featured a water-impermeable sarooj composed of lime, egg white, and bamboo dust.[2]
Another alternative formulation used for yakchal and water tanks in Iran uses "sand, clay, egg whites, lime, goat hair, and ash in specific proportions."[4] All of these examples utilize pozzolanic properties and/or incorporate biopolymerization to increase the durability and impermeability of the plaster.[5]