# The Mortars of Florence Riverbanks: Raw Materials and Technologies of _Lungarni_ Historical Masonry
## 1 Introduction  
Conservation of historical masonry building needs a thorough understanding of the physico-mechanical features and the sources of decay and vulnerability to preserve heritage integrity [1; 2; 3; 4; 5]. The study of historical masonry of riverbanks represents a multidisciplinary theme, which requires consideration of several aspects, among them the characterization of used materials, such as the mortars. The mortars influence the structural behavior of masonry, and their characterization is important to improve the knowledge of mechanical properties of civil architectural heritage walls. Several studies highlighted the relevance of these materials to acquire detailed information on the physico-mechanical behavior of the structure [6; 7; 8; 9; 10; 11] and to select the most suitable maintenance and restoration programs [12; 13; 14; 15]. The historic center of Florence (Italy), crossed by the Arno River, has suffered many geohydrorological disasters during history, due to floods, landslides, and riverbank failures [16; 17]. The current riverbank morphology of Florence is the result of urbanization, typical of centuries-old cities, which have been mainly developed along the river, and resources for many activities. On the other hand, the river may represent a threat. Indeed, the Arno River floods have damaged and destroyed millions of art masterpieces, rare books, and several monuments along the riverbanks area (named _Lungarni_). To mitigate the impact of geohydrorological hazards on cultural heritage and avoid the collapse of riverbanks, it is important to improve the knowledge of the properties of their constituent materials. Inparticular, evaluation of the physical and mechanical parameters of the building materials is necessary to assess their durability, degradation phenomena, and service life. The analysis of historical masonry walls is a complex task in terms of information about the inner core of the structural elements and for characterization of mechanical properties of the used materials and also due to their large variability. The different types of used mortars affect the masonry performance, allowing some degree of movement from creep or thermal effects without cracking. The mortar must be also sufficiently strong to develop an adequate adhesion to the elements [18] and to preserve the characteristic in time, especially in this case, in conditions of high humidity or even in an underwater environment. Chemical, mineralogical, and petrographic methodologies are often applied in order to obtain useful data for a complete characterization of binder, aggregate, and possible additives of mortars used in archaeological and architectonic heritage, but a few papers contain data on physico-mechanical characteristics [8; 19; 20; 21; 22; 23; 24; 25; 26]. Due to the difficulty of obtaining test samples of a suitable size for application of standardized physico-mechanical tests, in situ micro invasive methods are preferred [6; 27; 28; 29]. In this study, for the first time, a complete chemical, mineralogical, petrographic, and physico-mechanical characterization of the masonry of two Florence riverbanks (_Lungarno degli Acciuiuoli_ and _Lungarno delle Grazie_) is performed. The analyzed mortars belong to different portions of masonry of the riverbanks. The sampling was carried out to identify similarities or differences among phases, improving the knowledge of building technologies and raw materials used at different times. In fact, this methodology made it possible to identify four layers of masonry in the stratigraphy of the walls; two historical layers and two modern layers, post 1966, were discovered. Particular attention was paid to historical masonry that composes the lower portion of the riverbanks, a part that is subjected more to the extreme condition of complete saturation.