A novel approach to consolidation of historical limestone: the calcium alkoxides

Abstract

Abstract Potential utilization of calcium alkoxides as stone consolidants was considered. Reaction of Ca(OCH 3 ) 2 , Ca(OCH 2 CH 3 ) 2 (CH 3 CH 2 OH) 4 and Ca[OCH(CH 3 ) 2 ] 2 with the atmosphere in different experimental conditions was studied. The reaction produced CaCO 3 and two different pathways seem to be involved, the first taking place through CO 2 insertion into the Ca–O bond of Ca(OR) 2 species with formation of an alkylcarbonate derivative, subsequently transformed into CaCO 3 through ROH elimination; the second takes place through hydrolysis of Ca(OR) 2 to Ca(OH) 2 , which is then carbonated to CaCO 3 . The vaterite/calcite ratios found in the final CaCO 3 vary considerably with the experimental conditions adopted. Investigations demonstrated the potentiality of Ca(OCH 3 ) 2 to act as a stone consolidant. In fact, impregnation of a porous substrate, simulating the deteriorated stone, with a methanol solution of Ca(OCH 3 ) 2 , produced a crystalline vaterite film, which gradually filled all the pores and cavities of substrate and seems to fulfil the necessary requirements for a consolidant. Copyright © 2008 John Wiley & Sons, Ltd.