Ursachen der Festigkeit alter römischer und gothischer Gebäude und die Mittel, gleiche Dauerhaftigkeit bei neuen Mauerwerken zu erhalten / Reasons for the strength of old Roman and Gothic buildings and ways how to achieve the same durability with new masonry

The Preussian Royal Directorate for Finance, Military and Property has published the following prize question in 1775: in which way depends durability of Gothic and Roman masonry on time, on specific local conditions, on the stones and mortars used, and on the design, the execution and curing conditions? And how is new masonry to be built in order to achieve the same durability? The text which has been selected for this award is presented in full length in this contribution. First some observations made in Roman buildings are described. The observations are explained based on Roman literature on architecture and buildings. The durability of frequently used mortar and stones is discussed. The preparation of durable mortars is treated in detail. Different types of masonry are described. In conclusion it is stated that for external renderings and for mortars in masonry exposed to humid conditions cement mortar, i.e. mortar made with lime mixed with puzzolanas as a mineral binder, are to be applied exclusively. Internal renderings can be made with plaster of Paris or lime mortar. In an appendix it is pointed out that the thickness of a wall has a major influence on durability. In Holland durable and thin masonry walls are being built, however. This is possible because high quality cement mortars and bricks burnt at high temperature (clinkers) are used