• Wanja Wedekind

The secret of eternity

Ongoing research on traditional lime mortars and new course program

Many historical and ancient buildings are built with a lime mortar and testify to the durability of historical building techniques and traditional materials to this day. But not all lime mortars are the same. The secret of their durability lies in its production and processing technique and the choice of its aggregates.

Hot lime mortars are currently under discussion and their possible applications are manifold. However, the role of certain aggregates in connection with hot lime technology has not yet been sufficiently explored.

In a comparative study two early medieval cathedral ruins in Armenia were investigated in a research campaign for the Georg-August-University Göttingen/Germany. The main focus was on the investigation of historical masonry mortars.

The Zvartnots Cathedral was built from basalts and tuffs in the 7th century (Fig. 2, left). The Avan Cathedral is even older and was built in the 6th century, mainly from tuff (Fig. 2, right). In the study, that will be published in the proceedings of the 14th International Congress on the Deterioration and Conservation of Stone, the restoration history of both cathedral ruins were worked out and the petro-physical properties of the building stones were investigated. The historical and modern mortars used in both structures were analysed and examined in the laboratory. Onsite object investigations were carried out, which includes damage mapping, surface hardness, electrical conductivity and the sampling of salts. The investigation clarify the high quality and weathering resistance of the historical mortars. The mortars show a high strength and the formation of calcium silicate compounds and are comparable to the opus caementicium known in Italy from which, for example, the dome of the Pantheon (Figure 1) was constructed.

ACS is currently working on a new course program for the practical conservation of monuments and historical sites. One module of the course program will also deal with the various possible uses of lime in the history of architecture. These include mortar made from a lime putty, dry slaked sand-lime mortar and hot lime mortar in various applications (fresco technique, plaster mortar, masonry mortar, swelling mortar, hydraulic mortar). In addition, waterproof glossy plasters (stucco lustro, tadelakt etc.) and stucco mortars are explained.

If you are interested in further information about our course program, please send us a short mail.

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