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

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.

Potential of Advanced Consolidants for the Application on Sandstone

“…Another strategy involves the incorporation of elastic segments, such as hydroxyl-terminated polydimethylsiloxane (PDMS), into the xerogel structure; these segments effectively removed the stress caused by capillary pressure [5][6][7][8][9]. Another more general approach is based on the incorporation of various oxide nanoparticles, such as SiO 2 , TiO 2 , Al 2 O 3 and ZnO (so-called particle-modified consolidants, PMC) [3,8,[10][11][12][13][14][15]. Due to the increase in the pore size of PMC-based xerogel and the improvement of its mechanical properties, cracking was reduced, and the consolidation effect enhanced.…”

“…During the development of any novel consolidant, the selection of a suitable stone substrate is fundamental. Theoretically, three main substrates can be used: (i) a naturally aged substrate, (ii) an artificially aged substrate, and (iii) stone as quarried [15]. The first option provides the advantage of weathering under real world conditions and potentially reliable technological transfer into conservation practice.…”

Bioenergy and bioactive components in leaves of Toona sinensis

“…For example, it contains a large number of active ingredients which can be used in the field of bioenergy. Tetraethyl silicate, dibutyl phthalate, 1, 2, 3-propanetriol, 1-acetate are flammable liquids and may be used as biofuels [26][27][28]. The 2,2'-methylenebis 6-(1, 1-dimethylethyl)-4-methyl-phenol is widely used as antioxidant in natural rubber, rubber, latex, other synthetic materials and petroleum products.…”

Conservation of the Built Heritage: Pilot Site Approach to Design a Sustainable Process

“…Good practice in conservation recommends the preliminary testing of the restoration materials and methodologies in the lab and to base any decision on previously acquired experience. This is a cautious and widely recognized strategy, for which extensive data are available in the scientific literature describing the application of many different materials and products for cleaning, consolidation, and protection procedures, tested and assessed through standardized protocols in controlled lab conditions [21][22][23][24][25][26]. At the same time, only a few experiences of onsite testing and long term monitoring of conservation treatments are reported.…”