# The Mortars of Florence Riverbanks: Raw Materials and Technologies of _Lungarni_ Historical Masonry
## 5 Results and Discussion
### Final Remarks  
Previous studies on Florentine riverbanks are focused on the stabilization of walls following collapse events and on the geophysical survey and geotechnical characterization [16; 17], providing a reconstruction of the lithological sequence and defining the geotechnical characteristics of the materials involved in the failure. Other studies conducted on historic riverbanks in Italy, aimed at providing guidelines for conservation, propose a combination of on-site and laboratory investigations [57]. However, the minero-petrographical aspects are little deepened. Otherwise, in this study, we characterized the masonry of the Florentine riverbanks, deepening the minero-petrographic features, to evaluate the total properties and to estimate internal defects and inhomogeneities of the masonry. To summarize the minero-petrographic and physico-mechanical results, the following observations for each masonry type are reported:  
* Type X (historic mortar with decametric-sized coarse aggregates) is located both in the _Lungarno degli Acciaiuoli_ and in the _Lungarno delle Grazie_. The mortar consists of a natural hydraulic lime binder produced through traditional technologies, suggesting a historical origin. The last documented interventions on the riverbanks of _Lungarno degli Acciaiuoli_ and _Lungarno delle Grazie_ date back to the 13 th century, but probably some restoration works were realized in the past. The hydraulic characteristics allow hardening and preservation in time in conditions of high humidity or in an underwater environment. Figure 9: Diagram of correlation between \(\sigma\), \(\mathrm{Vp}\), and % of fine portion of core samples (**a**); \(\sigma\), \(\mathrm{Vp}\), and % of coarse aggregate (**b**). The riverbanks built with this masonry type are defined as \"core\" structures or rubble masonry. In general, the X samples are characterized by a natural hydraulic lime mixed with an aggregate with variable composition. The macroporosity is medium/high due to pores of irregular shape. From the physical tests carried out on the samples, it is observed that the effective porosity and the total imbibition coefficient are quite high (29.36% and 17.66%, respectively) as well as the capillary water absorption, which is medium-high (13.86 g/m\({}^{2}\)s\({}^{0.5}\)). Ultrasonic investigations return values compatible with materials characterized by good coherence and toughness. The amount of coarse aggregate estimated of this masonry type is medium/high (X has an average of 60% of coarse aggregate). The presence of decimetric-sized coarse aggregates does not represent a weakness of the material, since there is a good adhesion between the fine mortar fraction and the stone fragments. The mechanical strength average value obtained from the compression tests is about \(\sigma=24\) MPa, confirming the level of cohesion shown by the results of the ultrasonic tests. The physico-mechanical characteristics are suitable for carrying out the riverbank structural function. Although filling material is submitted when completely saturated, for the physical properties, the characterization results demonstrate masonry stability. * Type Y (historic mortar with centimetric-sized coarse aggregates) is located both in the _Lungarno degli Acciaiuoli_ and in the _Lungarno delle Grazie_; as in the X type, the mortar has natural hydraulic lime binder (obtained burning Pietra Albeeres, identified by under-burnt fragments) and historical origin. The core samples, which come from the higher portion of the riverbank wall, probably were built successively. High masonry was more probably destroyed during the floods. The minero-petrographic, effective porosity, and total imbibition coefficient results show for both types, X and Y, the same characteristics, so all masonry with type Y was composed of historical mortar. In fact, in the samples, lumps referring to Albeeres limestone were observed.