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

Abuel-ela, Reham

doi:10.21608/mjas.2021.103163.1028

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

نوع المستند : مقالات بحثية

المؤلف

reham abuel-ela

استاذ مساعد - قسم الترميم -کلية الفنون الجميلة - جامعة المنيا

10.21608/mjas.2021.103163.1028

المستخلص

In the last three decades, Ethyl silicate is currently the most widely used among stone consolidants; nevertheless, its reduced efficacy on calcitic substrates, where it exhibits some drawbacks that hinder their performance in terms of either mechanical efficacy, compatibility with the substrate and/or durability, make the research for alternative consolidants for carbonate stones necessary. This paper deals with a comparative study between limestone consolidants TEOS-based treatment and phosphate-based treatment severally. The idea of using phosphate-based treatments is forming calcium phosphates (ideally hydroxyapatite) as the reaction product between the substrate and an aqueous solution of a phosphate salt that the stone is treated with. The experimental study was conducted on limestone samples from Saqqara archaeological area, Egypt. Some tests were performed for studying the behavior of the consolidants used. The main aim of these tests is to estimate the consolidants efficiency and investigate the changes of physio-mechanical properties of the studied samples before and after consolidation. The obtained results showed that the hydroxyapatite treatment exhibits a good efficacy in terms of mechanical properties and, compared to treatment based on TEOS, it causes less pronounced alterations in open porosity and water transport properties. This makes the new treatment a potentially valid alternative to treatment based on Ethyl silicate, especially in those situations where the possible presence of water behind the consolidated layer (e.g. in case of rising damp, condensation or infiltration) might threaten the durability of the consolidation intervention.

نقاط رئيسية

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 .

الكلمات الرئيسية

الموضوعات الرئيسية

الترميم وصيانة الاثار

المراجع

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