pozzolana
noun
poz·zo·la·na ˌpät-sə-ˈlä-nə 
variants or pozzolan
ˈpät-sə-lən
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement
pozzolanic
ˌpät-sə-ˈla-nik -ˈlä-
adjective -ˈlä- 
Example Sentences
Recent Examples on the Web And so Giocondo built structures that mixed lime and pozzolana, as Vitruvius instructed. 
Jonathan Schifman, Popular Mechanics, 12 Oct. 2017 Clay was a major component, and a volcanic ash, today called pozzolana, was also used. Jonathan Schifman, Popular Mechanics, 12 Oct. 2017
Jonathan Schifman, Popular Mechanics, 12 Oct. 2017 Clay was a major component, and a volcanic ash, today called pozzolana, was also used. Jonathan Schifman, Popular Mechanics, 12 Oct. 2017 Word History
Etymology
Italian pozzolana
First Known Use
1684, in the meaning defined above