Wikipedia
Sarooj
Sarooj is a type of traditional Iranian water-resistant mortar, used in the construction of bridges, and ice pits or earth refrigerators ( yakhchal).
It is made of clay and limestone mixed in a six-to-four ration to make a stiff mix, and kneaded for two days. A portion of furnace slags from baths is added with fiber Louis (egg and straw) is added and newly fixed, then beaten with a 10 cm wooden stick for even mixing. Egg white can be used as a water reducer as needed.