## 3 Results and Discussion
### Mortars
The aggregate is, on average, abundant, mainly with homogeneous distribution (except in S5, which is the most superficial sample, and S10, S12, S13, which present heterogeneous grain size distribution) and well selected grain size composed of quartz, feldspars, mica, calcite, and fragments of carbonate rocks. The core samples extracted from the attic, samples S1, S2, S3, and S4, were obtained by mixing a natural hydraulic binder with an abundant aggregate (B/A 1/3-1/4), characterized by numerous lumps (Figure 9a) and heterogeneous structure and micritic/microsparitic texture (Figure 9b), with the exception of S3, which presents homogeneous structure and micritic texture (Figure 9c), and S4, which is composed by lower B/A, equal to 1/2-1/3. Lumps observed in the binder are useful for identifying the limestone burnt to obtain lime, which appears in the local Albheres limestone (Figure 9a). The aggregate has a homogeneous grain size distribution, ranging from 1 mm for rock fragments to 100 \(\upmu\)m for monocrystals. Quartz, plagioclase, rock fragments (quartzite, sandstones, calcarenie, micritic limestone), and few _cociopes_ fragments were identified under optical microscopy. The aggregate shape is sub angular, and a medium macropocosity due to pores of irregular shape was observed. In S4 (20-35 cm), the macroporosity is more developed (medium-high) and characterized by a recrystallized binder. Some differences in samples belonging to different core depths have been classified by grain size distribution and composition of aggregate, but the production of the binder has been the same. For core sample S5, which was obtained from the women's gallery, three samples extracted from different depths were investigated. Mortars were realized with a natural hydraulic binder, numerous lumps referred to the binder being not well mixed, and remnants of overburnt maryl limestones, identified as the local Albheres limestone, were observed (Figure 9d). All mortar samples suffered a strong recrystallization of the binder in the form of spathic calcite. In different depths of S5, some differences in the aggregate characteristics were present: S5 (7-12) cm was composed of abundant binder/aggregate (B/A 1/3) and fine grain size predominant, while S5 (12-26) cm and S5 (26-38) cm were characterized by less binder/aggregate (B/A 1/2-1/3), and a fine-medium size was predominant (Figure 9e). Furthermore, a different amount of carbonate rock fragment was registered, with respect to the attic mortar samples (a higher entity in S5 samples). For samples S6 to S17, belonging to the basement of the Baptistery, a binder made with natural hydraulic lime with a heterogeneous structure and micritic/microsparitic texture were observed. They show some differences: the binder of the S13 sample has a microsparitic texture (Figure 9f), and S14 has micritic texture (Figure 9g), while the binder of remaining samples has a micritic/microsparitic aspect (Figure 9h). The binder of the major parts of samples are characterized by a relevant recrystallization and heterogeneous structure. Some differences have also been registered in grain size distribution and aggregate composition for the same mortar core. A fair amount of carbonate rock fragments was registered, with abundant presence in S6, S10, S11, and S12 (S6 in Figure 9i). In the mortar basement samples, the aggregate has a homogeneous grain size distribution ranging from 800 \(\upmu\)m\({}^{-1}\) mm to 100 \(\upmu\)m, and in S10 and S13 a heterogeneous grain size distribution was observed (grain size 800-100 \(\upmu\)m). The aggregate shape is sub angular/sub rounded, with a high microporosity due to pores of irregular shape observed. In sample S12, coming from the basement and collected from the mosaic masonry, crushed ceramic (or _cociopesto_) was added to the mix consisting of air hardening calcite lime and fine quartzitic/carbonate aggregate, and the ratio of B/A is 1/2-1/3.