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Materials 2019, 12(1), 156; https://doi.org/10.3390/ma12010156

Efficiency and Compatibility of Selected Alkoxysilanes on Porous Carbonate and Silicate Stones

1
Institute of Geotechnics, Research Centre of Engineering Geology, Vienna University of Technology, 1040 Vienna, Austria
2
Institute of Art and Technology, Conservation Science, University of Applied Arts Vienna, 1010 Vienna, Austria
3
National Laboratory for Civil Engineering Lisbon, 1700-066 Lisbon, Portugal
*
Author to whom correspondence should be addressed.
Received: 1 December 2018 / Revised: 27 December 2018 / Accepted: 29 December 2018 / Published: 6 January 2019
(This article belongs to the Section Porous Materials)
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Abstract

This study compares the consolidation efficiency and compatibility of three selected alkoxysilanes on two porous carbonate and silicate substrates. Emphasis was given to artificially induced microstructural defects and subsequent restoration of mechanical and physical properties. Two newly engineered formulations (1) a TiO2 modified tetraethyl-orthosilicate in isopropanol with 70% active content and (2) a TiO2 modified alkyl-trialkoxysilane in isopropanol with 75% active content were compared to a commercial product (3), a solvent free tetraethyl-orthosilicate with 99% active content. Treatments were evaluated by scanning electron microscopy, mercury intrusion porosimetry, colour impact and their effect on dynamic modulus of elasticity, splitting tensile- and flexural strengths, capillary water absorption and water vapour permeability. A key outcome was that mechanical strength gain induced by treatments is primarily governed by a stone’s texture and microstructure, and secondarily by the gel deposition rate of consolidants. Likewise, the kinetics of the gel-forming reaction during curing is dependent not only on the product but also on the substrate. Therefore, the moisture related properties and the visual impact develop during time. There is no general trend on how it evolves in time, which can lead to incorrect interpretations of treatment compatibility. The results prove that wide-ranging treatment performance is obtained when applying the same products on different substrates. View Full-Text
Keywords: stone consolidants; tetraethyl-orthosilicate; ethyl silicate; TEOS; alkyl-trialkoxysilane; efficiency; compatibility; natural stone; mechanical testing; scanning electron microscopy stone consolidants; tetraethyl-orthosilicate; ethyl silicate; TEOS; alkyl-trialkoxysilane; efficiency; compatibility; natural stone; mechanical testing; scanning electron microscopy
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Ban, M.; Mascha, E.; Weber, J.; Rohatsch, A.; Delgado Rodrigues, J. Efficiency and Compatibility of Selected Alkoxysilanes on Porous Carbonate and Silicate Stones. Materials 2019, 12, 156.

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