The term pozzolan is derived from the ancient term Pozzolana, which refers to a volcanic ash (finely divided siliceous and aluminous material) found on the slopes of Mt. Vesuvius, adjacent to the small town of Pozzouli near the bay of Naples.
The Romans discovered that certain finely divided siliceous and aluminous materials when mixed with lime, produced cements having hydraulic properties, and up until two centuries ago these mixtures were the only cements that possessed the properties of hardening under water. The durability of natural pozzolan was proven in the construction of the Roman Empire buildings such as the Coliseum and the Aqueducts, which are still standing 23 centuries later. Earlier structures have been found in what was Mesopotamia, still intact now 40 centuries old, as well as, Alumina Silicate cast material found in the Mediterranean Sea, have withstood centuries of salt-water attack. The concrete bunkers in Iraq (old Mesopotamia) that could not be destroyed in the “91 Gulf War were built using natural pozzolan from Italy. In the United States the use of pozzolan with Portland cement concentrates dates back to 1910 in the construction of the Los Angeles Aqueduct. Other early examples of the use of imported pozzolan include the construction of the San Francisco Bay Bridge Piers and the Friant Dam.
Lassenite-SR is a natural siliceous (amorphous) mineral, made from the layers of diatoms and volcanic tuffs of Northern California's Cascade range. Lassenite Type N Pozzolan conforms to ASTM C-618, Federal Specifications #SS-C-1960/5 and CSA-CAN-A266-3M (Canadian) specifications for Type N (Natural) Pozzolan and meets specification requirements of the NRC for use on Nuclear Reactor Program, California Department of Water Resources, Corp of Engineers, U.S. Water and Power Resources Services, Cal Trans, Pacific Gas and Electric; Idaho Power and Arizona Public Service for hydraulic structures and power plants; Bechtel Corporation for hydraulic structures; municipalities for waste water treatment and transportation facilities.