Lime and Cement Plasters from 20th Century Buildings: Raw Materials and Relations between Mineralogical–Petrographic Characteristics and Chemical–Physical Compatibility with the Limestone Substrate

Abstract

This paper deals with the “modern” plaster mortars based on air lime, hydraulic lime, and cement used between the 1950s and 1990s of the last century, taking, as a case study, a historical building of the Cagliari city whose foundations and ground floor are cut into in-situ limestone. Different plaster layers (i.e., arriccio and intonachino, paint), applied on the excavated limestone walls, were collected from cave-room. All samples were analysed by optical and electron (SEM-EDS) microscopy and X-ray diffractometry (XRD) in order to define their microstructures, textures and compositional features. In addition, real and bulk density, water and helium open porosity, water absorption kinetic, and saturation index were measured. By microscopic imaging analyses, the binder/aggregate ratio as vol.% was determined. Results revealed that cement mortars, composed mainly of C-S-H, C-A-H, and C-F-H phases, given their high hydraulicity, low open porosity, and a rigid behaviour, showed a good chemical but not physical–mechanical adherence, as they were often found detached from the substrate and frequently loaded with salt efflorescence. On the contrary, the hydraulic lime-based mortars, characterised by a binder composed of C-S-H and C-A-H phases and calcite derived from the portlandite carbonation, showed a greater affinity with limestone substrate and other plasters. Thus, they are more suitable to be used as a repair mortar, showing a long durability on the time. The thin air lime-based plasters (intonachino) showed a good adhesion to the substrate, exerting their coating function better than the harder, cement-based mortars. Lime-based wall paints have a good chemical adhesion and adaptability to the irregular surface of the substrate, due to low thickness of lime paint layers (<1 mm) that confers an elastic physical behaviour.

Geological and archaeological heritage in the Mediterranean coasts: Proposal and quantitative assessment of new geosites in SW Sardinia (Italy)

“…This area was extensively populated, especially in the Phoenician-Punic and Roman periods, with various settlements on the coast where the Frontiers in Earth Science frontiersin.org remains of the ancient village of Bithia (Bartoloni, 1996) on the promontory of the Chia tower (Torre di Chia), the harbor at Capo Malfatano area, and the ancient quarries of Piscinnì, with the extractive fronts still intact and recognizable, can still be seen today. These archaeological sites are part of a wider itinerary of the south-western part of Sardinia, starting from Cagliari (e.g., Roman amphitheater, Early Christian San Saturnino Basilica, Romanesque Cathedral and others; Columbu et al, , 2018Columbu et al, , 2022 to the Punic-Roman site of Nora, which preserves buildings and materials of a high historical value (i.e., theater, thermal baths; Columbu and Garau, 2017;Columbu, 2018;Columbu et al, 2019), to the important Phoenician-Punic settlements of Monte Sirai (Bartoloni, 2000;Perra, 2009), Sulki village (today Sant'Antioco) (Bartoloni, 1988;Pompianu, 2010), Antas site with Punic-Roman Temple (Columbu et al, 2021), and several Nuragic structures in the westernmost part where several archaeological finds have been found as well as in other areas of Sardinia (Bertorino et al, 2002). In addition to the civil settlements of classical age, several coastal watchtowers [i.e., the towers of Chia (near the village of Bithia), Capo Malfatano, Capo Spartivento, and Piscinnì] built around the 16th to 17th centuries constituted a unique defensive system, transformed into a cultural and tourist network today and appreciated and visited by hundreds of tourists.…”

Characterization of Pore Size Distribution and Water Transport of UHPC Using Low-Field NMR and MIP

“…Generally, the compressive strength increased with SF and MK volume. This is attributed to the filling effect and high pozzolanic activity of SF and MK [ 36 , 37 , 38 , 39 , 40 , 41 ].…”

SiO2 Nanoparticles as New Repairing Treatments toward the Pietraforte Sandstone in Florence Renaissance Buildings

“…For this reason, conservation scientists have thought and designed new materials based on silicates, but with different properties that derive directly from the dimensions confined in the nanoscale, as the different dispersibility in several different working mediums, generating a nanosuspension and not a consolidating agent in a solvent. According to what has been said previously, several nanoparticles have been synthesized and applied to Florentine sandstones by many authors in literature, such as SiO 2 [8][9][10][11], Ca(OH) 2 /nano lime [12][13][14], CaCO 3 [15,16], nanocomposite materials [17,18] and hybrid nanocomposite materials based on consolidating agents and biocide, as reported in the literature [19].…”