Kirmenjak -: Pietra d'Istria:: a preliminary investigation of its use in Venetian architectural heritage

Kirmenjak - white limestone from the quarries near the village of Kirmenjak in Istria (Croatia), in the past known as Pietra d'Istria - has been regularly used in the construction of the basal zone of Venetian buildings since the 14th century. Its characteristics - durability, extremely low water absorption and high compressive strength - made it an ideal material for the lowest parts of Venetian buildings in the zone between foundation (wooden piles) and brick walls. In this zone, exposed to tidal flooding and low-tide drying, materials deteriorate very quickly, but Kirmenjak has proved to be durable even in this aggressive saline environment. Moreover, this dense micritic or pelmicritic stylolitized limestone from the Upper Jurassic (Tithonian) was used as an efficient barrier to rising damp. Preliminary in situ investigation of how Kirmenjak blocks were laid shows that the prevalent stylolite orientation is horizontal in the basal parts of buildings, while in other structural elements this orientation varies. This inspired the hypothesis that the Venetian constructors took advantage of horizontally laid stylolite discontinuities (partially filled with clay) as a multilayer humidity barrier.