Abstract
A treatment for both protection and consolidation, was synthesized in a simplified procedure through the sol gel process. Synthesized nano-calcium oxalate (CaOx) was incorporated into tetraethoxysilane (TEOS) and polydimethylsiloxane (PDMS), providing a hybrid hydrophobic consolidant nanocomposite. Oxalic acid was selected due to its ability to catalyse the hydrolysis of TEOS, as a drying control agent, but also because of its contribution at the formation of the calcium oxalate in reaction with calcium hydroxide. CaOx, incorporated into the silica matrix of the final copolymer, exhibits interfacial compatibility with the stone substrate and simultaneously strengthens the treated surface, since CaOx appears to be more stable than calcium carbonate. The hydrolysis of TEOS, as well as the formation of CaOx was evaluated through thermogravimetric analysis (TG/DTA). The nanocomposite consists of particles with approximately 7–700 nm in size range, as shown in TEM images. The consolidation, in combination with the hydrophobicity of surface resulted in an increase of the resistance to decay. Mechanical properties were enhanced as evaluated by ultrasonic pulse velocity on treated and untreated surfaces. Furthermore, water contact angle, as well as water absorption by capillarity test, showed improved water repellency of treated stones. Finally, this treatment doesn’t alter the aesthetic surface parameters, a fact that is essential in cultural heritage conservation, while the consolidant remains intact under UV and moisture exposure.
Highlights
In order to preponderate these drawbacks, we designed a modified TEOS based consolidant nanocomposite; calcium oxalate (CaOx) has been integrated into silica matrix, in order to achieve chemical affinity with the carbonaceous nature of limestones. It is well-known that calcium oxalate has played a crucial, protective role in monuments, since quantity of it has been detected in the patina, present on historical surfaces that have been maintained in fairly good conditions [5,6]
Color parameters as well as physical and mechanical properties and microstructure of the samples were checked through colorimetry, digital microscopy, contact angle, water capillarity and ultrasound pulse velocity tests
TiO2 Nanocrystal Based Coatings for the Protection of Architectural Stone: The Effect of Solvents in the Spray-Coating Application for a Self-Cleaning Surfaces
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In order to preponderate these drawbacks, we designed a modified TEOS based consolidant nanocomposite; calcium oxalate (CaOx) has been integrated into silica matrix, in order to achieve chemical affinity with the carbonaceous nature of limestones It is well-known that calcium oxalate has played a crucial, protective role in monuments, since quantity of it has been detected in the patina, present on historical surfaces that have been maintained in fairly good conditions [5,6]. The aforementioned product was applied on porous limestones called “alfas” origistones for monument reconstruction This type of limestone is very porous, with massive nating from a specific quarry of the island of Crete and are commonly used as building texture, whereas its open porosity has been measured equal to 17.92% (±1.58) [Error!
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