Nanolime for the consolidation of lime mortars: A comparison of three available products

Abstract

Nanolime products are one of the most promising consolidation methods for historic calcareous substrates. Whilst the popularity of nanolime has been growing, its consolidation mechanism still needs to be fully understood when applied to highly porous substrates. The aim of this paper is to compare the three available nanolime products in terms of consolidation efficacy on lime mortar specimens. It is shown that repeated applications of a low concentrated nanolime can increase the superficial cohesion and the mechanical strength of the mortar within 1cm from the surface, while also reducing porosity, number of micro-pores and capillary water absorption coefficient. Nanorestore Plus® yielded the highest short-term consolidation effect. However, L'Aquila nanolime showed a higher durability which was attributed to a better developed crystalline structure.

Sticky rice–nanolime as a consolidation treatment for lime mortars

“…The water/binder ratio was 1.56 to obtain a constant flow of 16 cm measured according to BS EN 1015-3:1999 [31]. The mixing and casting procedure of the mortar can be found elsewhere [24]. Mortar beams (40 9 40 9 160 mm) were de-molded after 5 days and then stored in an outdoor sheltered area (T & 5-15°C, R.H & 60-80%) for 28 curing days.…”

“…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.…”

“…The nanolime dispersion was applied 2 days after its synthesis to increase its effectiveness [40]. The nanolime dispersion was agitated before application to increase the colloidal stability of the particles [24]. The application was ended when no further absorption was observed (surface remains completely wet for a period of at least 1 min).…”

“…A complete description of the application method of nanolime can be found elsewhere [24]. Upon treatment completion, the treated samples were stored for 28 days at outdoor environment conditions (70 ± 5% RH, T = 10 ± 5°C).…”

“…Due to its high reactivity and compatibility, nanolimes resulted in successful superficial consolidation of historic substrates such as wall-paintings [21][22][23]. However, when an in-depth consolidation is required, their effectiveness is controversial since rarely do nanolimes attain penetrations above 1 cm [24]. Some studies focused on different ways to improve the nanolime in-depth consolidation effectiveness, for example, Daniele et al [25] achieved faster and deeper consolidation by adding sodium bicarbonate (NaHCO 3 ) to the nanolime alcohol solution.…”