Mineral Consolidants

Inorganic consolidants, such as ethyl silicate, nanolime and ammonium oxalate, have proven to be effective for certain materials, but each has its drawbacks. This has recently led to the investigation of hydroxyapatite (HAP) as a novel inorganic consolidant, which demonstrated excellent performance on carbonate stones. Considering that a mineral that matched calcite crystal lattice parameters even more closely than HAP would be expected to provide a consolidating action even greater than HAP, in this study aluminum phosphate (AP) was investigated as a potential new consolidant. Indeed, AP has lattice parameters differing from those of calcite by only 1%. The consolidating ability of AP was preliminarily investigated here in comparison with HAP. Both treatments were tested on artificially weathered marble samples, in the view of their application for conservation of sugaring marble. A novel method is also proposed for producing samples with near-surface damage similar to that of sugaring marble in the field. The results of the study point out that the novel weathering method is able to provide samples with tailored gradient in dynamic elastic modulus, closely resembling naturally sugaring marble. The AP treatment was found to significantly improve the dynamic elastic modulus of weathered marble, at least as efficiently as the HAP treatment investigated in this study. This confirmed the high potential of AP as a new inorganic consolidant.