£19.50 exc. VAT

Trass is a reactive natural pozzolanic additive. Pozzolans improve the strength and durability of lime mortars. Pozzolans are defined as materials which, though not cementitious in themselves, contain constituents which will combine with lime at ordinary temperatures in the presence of water to form stable insoluble compounds possessing hydraulic properties.

Trass is ground ‘tuffstein’ from the Rhine valley in Germany. Tuffstein is a rock-like compacted tuff of volcanic dust and ash. Rhenish trass has been known for some 2000 years, and mortars containing trass have been found in old Roman buildings along the Rhine. It has been increasingly used in lime mortars since the early 18th century, and was experimented with by John Smeaton in 1756 for the Eddystone lighthouse, although an Italian pozzolana from ‘Civita Vecchia’ was ultimately used.

This is sold in 40kg bags and cannot be sent via courier due to weight limitations. Due to this, please select one of the pallet options available. 

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Additional information


Trass is a reactive natural pozzolanic additive for addition to lime mortars to improve strength and durability.

Shelf Life

Indefinite stored in dry condition.


Fine creamy grey powder. Batch colour varies slightly.


To be mixed with lime mortar immediately before use. Add at 5%, 7.5%, or 10% by volume to mortar depending on the particular circumstances. Do not remix setting mortar. Fine powders of nuisance dust classification. Use gloves, overalls, face and dust masks, and respiratory protection as appropriate to working environment. Avoid direct contact with eyes or skin.


Ex. Stock.