Pozzolana

(also pozzuolana or pozzolan), rocks consisting of loose products of volcanic eruptions (ash, tuffs, pumice). Owing to its hydraulic activity (the absorption of milligrams of CaO from 1 g of lime solution), pozzolana is used as a hydraulic additive in the production of binding materials called pozzolana cements. Similar hydraulic cements are called trasses. Large deposits of pozzolana are located in Italy. In the USSR deposits of pozzolana and trass are found in the Northern Caucasus (city of Nal’chik), in the Crimea (Mount Karadag), and the Armenian SSR.