Trass is the local name of a volcanic tuff occurring in the Eifel, where it is worked for hydraulic mortar. It is a grey or cream-coloured fragmental rock, largely composed of pumiceous dust, and may be regarded as a trachytic tuff. It much resembles the Italian pozzolana and is applied to like purposes.

What are tras with in construction?

A light-colored tuff used in hydraulic cement. [Dutch tras, short for obsolete terras, tiras, possibly from Italian terrazzo, stone chips; see terrazzo.]

How do you spell Trass?

Trass, tras, n. a volcanic earth used as a hydraulic cement. After it has been quarried it is ground in mills, and used for cement stone under the name of trass.