Abstract
The main idea of the European STONECORE R&D project (2008 to 2011) was to develop and evaluate nano materials for the use in refurbishment and conservation of historic monuments. A set of different calcium hydroxide (“lime”) nanoparticles dispersed in alcohols (CaLoSiL®) available on the market were tested. The general advantages attributed to alcoholic lime dispersions were: compatibility of the consolidant with the original building material, no limitation of penetration due to the particle size, and no mobilisation of soluble salts. The paper mainly reports the evaluation of lime nanosols for consolidation of lime mortar, gypsum stucco, and mural painting layers. In order to achieve a penetration behaviour which is adequate to the pore structure of the substrate, the composition of the nanosol as well as its application procedure had to be adjusted. This could be achieved by dilution, additives, or after-treatment of the surface. Apart from structural strengthening of porous structures the lime nanosols were tested for treatment of larger defects such as fissures, cracks, detachment, and delamination. For this purpose the nanosols were modified with additives, fillers, and aggregate. The developed lime nanosol formulations were applied to test sites at three historic monuments with promising results. A ‘modular system’ was developed to meet all these conservation needs. These materials showed sufficient adhesive strength. They proved applicable for the consolidation of severely cracked limestone as well.
Highlights
The main idea of the European STONECORE R&D project (2008 to 2011) was to develop and evaluate nano materials for the use in refurbishment and conservation of historic monuments
The investigation of the mortar specimens treated with calcium hydroxide nanosol has shown the accumulation of calcium hydroxide at the surface after evaporation (Figure 3)
In order to improve the distribution of the nanosol into the mortar and to avoid white haze on the surface, the application method was modified in four directions: Figure 2 Three-point bending strength of weak gypsum lime mortar before and after treatment with CaLoSiL nanosols: 0 = untreated, 1–6: E25 (3 applications), 1–7: IP25 (3 applications), 1–8: NP25 (3 applications), 2–2: E25, diluted with ethanol, increase of concentration during 6 applications (5/7.5/10/12.5 15/25 g/L), 3–2: E50 diluted with acetone and ethanol (60%/40%), 6 applications (12.5 g/L), 4–2: E50 diluted with acetone and ethanol (60%/40%), increase of concentration during 6 applications (5/7.5/10/12.5 15/25 g/L)
Summary
The main idea of the European STONECORE R&D project (2008 to 2011) was to develop and evaluate nano materials for the use in refurbishment and conservation of historic monuments. Conservation of historical buildings, sculptures or wall paintings requires materials which are compatible with the components originally used for construction. This means that the characteristics and behavior of the original system has to be respected and should not be substantially changed, especially in terms of porosity, stability and retreatability. The idea was to develop and test nano-materials compatible to those used during construction. The development and testing of calcium hydroxide nanosols was accompanied by comprehensive research in the field of non-damaging assessment methods
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