Calcium alkoxides for stone consolidation: investigating the carbonation process

During the European NANOMATCH project (funded under FP7 GA no. 283182) two alkoxides, calcium tetrahydrofurfuryloxide and calcium ethoxide, were developed and tested as new products for stone and stone-like consolidation [1, 2]. Their behavior in atmosphere makes them suitable products for conservation of calcareous stone: in fact they react with humidity and carbon dioxide to give CaCO3. In this paper we report the results of an investigation aimed to understand the influence of different parameters (RH, solvents, concentration) on the carbonation process and on the formation of the final coating, in particular as far as the crystalline form is concerned (vaterite, calcite, portlandite). Solution of alkoxides in different solvents (different alcohols, n-butylacetate, ligroin) were prepared at two concentrations (5g/L and 20g/L in Ca). Kinetic of carbonation was investigated through ?-FT-IR. The solutions were then applied on glass slides and maintained two weeks either at environmental conditions or at controlled RH conditions (50% and 90%). The resulting coatings were then characterized by ?-FT-IR, XRD and SEM. Results indicate that the most important factors influencing the kinetic and the final products are the humidity and the features of the employed solvents. [1] I. Natali, P. Tomasin, F. Becherini, A. Bernardi, C. Ciantelli, M. Favaro, O. Favoni, V. J. F. Pérez, I. D. Olteanu, M. D. R. Sanchez, A. Vivarelli, A. Bonazza, Innovative consolidating products for stone materials: field exposure tests as a valid approach for assessing durability. Heritage Sci., 3 (6), 2015. [2] M. Favaro, M. Chiurato, P. Tomasin, F. Ossola, N. El Habra, N. Brianese, I. Svensson, E. Beckers, V. Forrat Pérez, M. Romero Sánchez, G. Orial, E. Bourguignon, A. Bernardi, Alkaline earth alkoxides for conservation treatment of stone and wood in built heritage. In Proceedings of 3rd European Workshop on Cultural Heritage Preservation (EWCHP) Bolzano, Italy. 2013.