MECHANICAL CHEMICAL-PHYSICAL CHARACTERISATION OF BRICKS AND MORTARS OF THE 13th CENTURY USED FOR THE CONSTRUCTION OF THE BASILICA OF SAN FRANCESCO IN ASSISI

摘要

The tests carried out on the bricks coming from the Basilica of San Francesco in Assisi revealed a good preservation state of the samples ; the time passed from their manufacture hasn't caused any apparent degradation on the materials. The chemical study of their composition enabled verification of how raw materials used for the manufacture of the bricks were chosen centuries ago. The selection of special soils (reactive clays) mixed with calcareous marns is the "secret" of their nature, whereas the baking at high temperatures, although definitely below 1000 °C, is the "secret" to their mechanical characteristics. The mortars used for installing the bricks reflect the knowledge and the techniques used at the time of their construction. These analyses enabled the identification of the "original" chemical composition. These mortars are mainly composed of common lime mixed with reactive materials such as clays. This paper has to be intended as a preliminary work which, through the knowledge of the ancient materials used for the construction of the building, can help us choose the most suitable products for the repair.