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Open AccessArticle

Conservation of Monuments by a Three-Layered Compatible Treatment of TEOS-Nano-Calcium Oxalate Consolidant and TEOS-PDMS-TiO2 Hydrophobic/Photoactive Hybrid Nanomaterials

School of Architecture, Technical University of Crete, Polytechnioupolis, Akrotiri, 73100 Chania, Crete, Greece
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Materials 2018, 11(5), 684; https://doi.org/10.3390/ma11050684
Received: 12 March 2018 / Revised: 16 April 2018 / Accepted: 25 April 2018 / Published: 27 April 2018
(This article belongs to the Special Issue Selected Papers from TechnoHeritage 2017)
In the conservation of monuments, research on innovative nanocomposites with strengthening, hydrophobic and self-cleaning properties have attracted the interest of the scientific community and promising results have been obtained as a result. In this study, stemming from the need for the compatibility of treatments in terms of nanocomposite/substrate, a three-layered compatible treatment providing strengthening, hydrophobic, and self-cleaning properties is proposed. This conservation approach was implemented treating lithotypes and mortars of different porosity and petrographic characteristics with a three-layered treatment comprising: (a) a consolidant, tetraethoxysilane (TEOS)-nano-Calcium Oxalate; (b) a hydrophobic layer of TEOS-polydimethylsiloxane (PDMS); and (c) a self-cleaning layer of TiO2 nanoparticles from titanium tetra-isopropoxide with oxalic acid as hole-scavenger. After the three-layered treatment, the surface hydrophobicity was improved due to PDMS and nano-TiO2 in the interface substrate/atmosphere, as proven by the homogeneity and the Si–O–Ti hetero-linkages of the blend protective/self-cleaning layers observed by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The aesthetic, microstructural, mechanical and permeabile compatibility of the majority of treated substrates ranged within acceptability limits. The improved photocatalytic activity, as proven by the total discoloration of methylene blue in the majority of cases, was attributed to the anchorage of TiO2, through the Si–O–Ti bonds to SiO2, in the interface with the atmosphere, thus enhancing photoactivation. View Full-Text
Keywords: conservation; monuments; nanostructured; TEOS-nano-Calcium Oxalate; PDMS-SiO2-TiO2 nanocomposite; compatible; hydrophobic; self-cleaning; limestone; cement mortars conservation; monuments; nanostructured; TEOS-nano-Calcium Oxalate; PDMS-SiO2-TiO2 nanocomposite; compatible; hydrophobic; self-cleaning; limestone; cement mortars
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MDPI and ACS Style

Kapridaki, C.; Verganelaki, A.; Dimitriadou, P.; Maravelaki-Kalaitzaki, P. Conservation of Monuments by a Three-Layered Compatible Treatment of TEOS-Nano-Calcium Oxalate Consolidant and TEOS-PDMS-TiO2 Hydrophobic/Photoactive Hybrid Nanomaterials. Materials 2018, 11, 684.

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