The biocalcarenite stone of Agrigento (Italy): Preliminary investigations of compatible nanolime treatments

Abstract

Nanolime is a promising consolidant for the conservation of most historic structures thanks to its high compatibility with carbonate-based substrates. Nanolime can recover the superficial cohesion of deteriorated surfaces thanks to its potential to complete the carbonation process, recreating a thin network of new cementing calcium carbonate. In this paper, the nanolime was produced by an innovative, time and energy-saving and scalable method, and its efficacy was tested preliminarily on biocalcarenite stones from Agrigento. The stones characterization as well as the treatment effectiveness, in terms of protection against water and superficial consolidation, was investigated by several techniques such as X-ray fluorescence, X-ray diffraction, scotch tape test, water absorption by capillarity, mercury intrusion porosimetry, drilling resistance measurement system and colorimeter. Investigations showed that nanolime could guarantee a complete transformation in pure calcite together with a superficial consolidation and a reduction in water absorption.

Tuning the Dimensionality of Nano Ca(OH)2 with Surfactants for Wall Painting Consolidation

“…XRD was performed to study the crystal structural evolution with the surfactant additions (Figure (b)–(d)). As shown in Figure (i), all the peaks agreed well with the Ca(OH) 2 characteristic peaks (JCPDS card no.44‐1481) . Furthermore, intensities of peaks for (0001) and of Ca(OH) 2 gradually decrease when the volume percentages of DMF and OPPE increase from none (none added) to 30% and 30%, and then to 50% and 50% (Figure (j)).…”

“…As shown in Figure 2(i), all the peaks agreed well with the Ca(OH) 2 characteristic peaks (JCPDS card no.44-1481). [25] Furthermore, intensities of peaks for (0001) and ð1010Þ of Ca(OH) 2 gradually decrease when the volume percentages of DMF and OPPE increase from none (none added) to 30% and 30%, and then to 50% and 50% (Figure 3(j)). It should be noted that at room temperature, nano Ca(OH) 2 can be facilely and economically synthesized on a larger scale (650 ml, 5 mg/ml) and high yield (99.3%) in~5-10 seconds ( Figure S5).…”

Sticky rice–nanolime as a consolidation treatment for lime mortars

“…Nanolime was synthesized through an anionic exchange process carried out at room temperature and ambient pressure by mixing under moderate stirring an anion exchange resin (Dowex Monosphere 550A OH by Dow Chemical) with an aqueous calcium chloride solution (CaCl 2 by Sigma-Aldrich), as described in the literature [34,35]. After the synthesis, the newly synthetized nanoparticles of Ca(OH) 2 were dispersed in a 50-50% isopropanol/water solvent maintaining the concentration at 5 g/L, as this was found to be the optimal alcohol/water ratio [24,35]. A description of morphology, reactivity and colloidal stability of this nanolime can be found in the latter reference.…”

Inorganic Nanomaterials for Restoration of Cultural Heritage: Synthesis Approaches towards Nanoconsolidants for Stone and Wall Paintings

“…Depending on the solvent, the environmental RH, and the concentration, they form pure calcite in a few hours or up to 7 days. NPs prepared by this method and dispersed in water/2‐propanol (1:2; 5 and 10 g L −1 ) and water/1‐butanol (1:20; 5 g L −1 ) have been applied as consolidants by brushing on decayed biocalcarenite stones until saturation . These stones were used as building materials for most buildings of the “Valley of the Temples” in Agrigento, Sicily, Italy.…”

“…A complete carbonation process occurs in the first 30 min and leads to the formation of calcite as a pure and unique phase that is fundamental for assuring compatibility with the treated surface. Treatment of the stone surface three times with 10 g L −1 nanolime in water/2‐propanol (W/A=50 %) is reported to be the most efficient formulation acting as a superficial consolidant, and it increases the superficial cohesion, reduces porosity, and enhances the mechanical properties in the first 10 mm beneath the surface …”