EVALUATION OF REMEDIAL EFFICIENCY OF PHOSPHATE-BASED TREATMENT IN STRENGTHENING MONUMENTAL LIMESTONE IN COMPARISON WITH TEOS-BASED TREATMENTS, A CASE STUDY

As of their extended use in historical buildings and architecture, the consolidation of weathered carbonate stones, such as limestone and marbles, is a key goal in cultural heritage conservation and many experimental studies have been aimed at improving the existing consolidating treatments and developing materials (micro and nano) compatible with natural and artificial stone

Consolidants must fulfill many requirements not only in terms of consolidating efficacy (ability to recover the cohesion of the decayed material), but also in terms of compatibility with the substrate (i.e. should not cause any damage to the substrate or adjacent material) and, at the same time, be durable. From this point of view, inorganic consolidants seem quite attractive, as they are generally stable and durable

Stone consolidation needs careful designing and preliminary testing, as it is basically an irreversible intervention in most cases . Moreover, consolidation might even result in an acceleration of materials decay, if unsuitable materials or treatment conditions are selected. For these reasons, the study of stone consolidants is of primary importance

Consolidants based on alkoxysilane precursors are commonly employed in the preservation of stonework . The alkoxysilanes and alkyl alkoxysilanes, or “silanes” for short, have undoubtedly been the most widely used stone consolidants over the past thirty years . An advantage of these materials over organic polymers is that they are applied as low molecular weight monomers or oligomers that polymerize to form consolidants inside the stone. The implicitly low viscosities of the starting materials greatly improve penetration depths. In this study, one of the simplest alkoxysilanes employed in commercial formulations was selected, tetra-ethoxysilane or tetraethyl orthosilicate (TEOS), also known as ethyl silicate .