The Collaborative International Dictionary
Pozzuolana \Poz`zu*o*la"na\, Pozzolana \Poz`zo*la"*na\, n. [It.] Volcanic ashes from Pozzuoli, in Italy, used in the manufacture of a kind of mortar which hardens under water.
Wiktionary
n. A type of volcanic ash used for mortar or for cement which sets under water.
Wikipedia
Pozzolana, also known as pozzolanic ash (pulvis puteolanus in Latin), is a siliceous or siliceous and aluminous material which reacts with calcium hydroxide in the presence of water at room temperature (cf. pozzolanic reaction). In this reaction insoluble calcium silicate hydrate and calcium aluminate hydrate compounds are formed possessing cementitious properties. The designation pozzolana is derived from one of the primary deposits of volcanic ash used by the Romans in Italy, at Pozzuoli. Nowadays the definition of pozzolana encompasses any volcanic material ( pumice or volcanic ash), predominantly composed of fine volcanic glass, that is used as a pozzolan. Note the difference with the term pozzolan, which exerts no bearing on the specific origin of the material, as opposed to pozzolana, which can only be used for pozzolans of volcanic origin, primarily composed of volcanic glass.
Usage examples of "pozzolana".
The hydraulic grade cement, the sifted sand with its carefully measured moisture content, the pozzolana and other arcane chemicals, and a precisely measured amount of water.
The modern EB suggests addition of small amounts of lime, portland cement, pozzolana, or bitumen to the top eight to twenty inches of the ground.