Archaeology of Architecture Research Papers (original) (raw)

Great differences exist in the composition and quality between the ancient mortars of the classical antiquity and those of Middle Ages, not only due to the different usage of the mortars, but also because of the progressive lost of knowledge about mortars' production techniques, from the time when Cato, in the 2nd Century BC, and Vitruvius, in the 1st Century BC, clearly stated how a good mortar should be prepared. These differences have been found also in the ancient mortars of the Medio Volturno River area, analyzed by several different mineralogical, chemical and microscopic (SEM/EDX, XRPD with Rietveld analysis, TGA, FT-IR, thin sections analyses) techniques. We characterized several ancient mortar samples, showing that, during the classical Roman period, the Vitruvius' suggestion of using "pure carbonate rock" was the standard practice, not only for the binder, but also for the aggregate part of mortars, in particular for public buildings, such as bridges and city walls. On the contrary, during the Middle Ages it was common to use other raw materials with lower percentage of carbonate rocks, such as feldspars and other volcanic minerals, typical of the region Campania areas, rich in volcanic sediments, and also some amorphous materials, such as ground bricks, and glassy volcanic stones. It is also frequent to find poor quality medieval mortars, because of the low quality of the raw materials from one side, and because of the often hurried binder preparation process, resulting in more friable mortars and, consequently, in less durable walls.