Study of calcium ethoxide as new solution for the consolidation of carbonate stones

The combined action of several physical, chemical and biological factors cause the weathering of stone widely employed in the field of Cultural Heritage. These deterioration processes are well studied and the results have promoted the research of compatible, efficient, stable and long-lasting consolidation treatments to overcome the limitations of traditional ones and to meet the requirements of the historic building substrates. Within this context, during the European collaborative project NANOMATCH, different consolidating agents for carbonate supports, as calcium alkoxides, were synthesized and applied. The present works aimed at studying the properties and, especially, the effectiveness of one of these products - calcium ethoxide - as stone consolidant. This product is considered a promising alternative to traditional treatments for the consolidation of carbonate stones, since it meets one of the key requirements in the field of conservation of Cultural Heritage, such as the chemical compatibility with the support. In fact, calcium ethoxide, dissolved in a proper organic solvent, penetrates within the porous substrate and, reacting with moisture and carbon dioxide of the atmosphere, forms a calcium carbonate coating on the pore walls. The investigation started with a first characterization of calcium ethoxide diluted in different solvents - chosen for their different boiling point and because they are actually used in the restoration field - through a study of the carbonation process: its kinetics, reaction pathway and evaluation of mineralogical phases formed at the end of this process. Subsequently, the consolidant was applied on carbonate stones with different total open porosity value and a multi-technique approach was used for the assessment of its performance - compatibility and efficacy - as consolidating agent, by comparison with a commercial product This work has revealed important information regarding the influence of environmental conditions and used solvent on the carbonation process of calcium ethoxide and therefore, on its potential as consolidating treatment for carbonate supports.