Get this from a library! Alkoxysilanes and the consolidation of stone. [George Wheeler; Getty Conservation Institute.]. Stone is one of the oldest building materials, and its conservation ranks as one of the most challenging in the field. The use of alkoxysilanes in the conservation. Permalink: ; Title: Alkoxysilanes and the consolidation of stone / George Wheeler ; with annotated bibliography by.
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Adobe building materials are made by mixing sand, silt and clay with water to an adequate plasticity so that it can be formed in wooden molds or used as mortar or plaster. The amount of consolidant deposited in each of the treated masonry samples is determined to evaluate the effectiveness of the treatment and efficiency of the application procedures.
Conservation of Historic Buildings. Therefore, waxes can be considered as protective coatings rather than impregnants. The Deterioration and Conservation of Stone. Centro per la Conservazione delle Sculture all’Apeno,pp.
For example, alkoxysilanes are rather expensive materials. Internet resource Document Type: The penetration of 5 cm. The combination of water with gaseous pollutants results in acidic precipitation.
If so, a retreatment with ethyl silicate to regain the required degree of consolidation might be a possibility, but only if the material has regained its original porosity. The network polymer that first forms is a soft gel; the gel shrinks and becomes harder; the shrinkage continues and it changes into a hard, brittie glass; in the end, it shrinks to small, glassy particles or crumbles to a fine powder.
These observations also confirmed the slowness of the hydrolysis reaction, although the results alokxysilanes this study are considered preliminary due to the short time range.
Grissom and N R. Please choose whether or not you want other users to be able to see on your profile that this library is a favorite of yours. This desirable property for a consolidant provides ethyl silicate with excellent penetration in porous materials. Larson claimed that silanes make very good deep consolidants, but poor surface consolidants, whereas acrylics are known as good alkoxyilanes consolidants, but are not effective for consolidation in depth.
Alkoxysilanes and the consolidation of stone (Book, ) 
For example, the addition of ethyl acrylate or butyl methacrylate to methyl methacrylate improves chemical strength, hardness and weathering. Marsh, crystalline inorganic precipitates, such as barium carbonate and barium sulfate, do not have a long- term consolidating effect.
Additionally, all repairs to the masonry should be completed before the consolidating agent is applied because treated surfaces will not bond to cementitious or synthetic repair materials. Silica SiOj is an inorganic compound of the chemical element silicon Si.
If an alkoxysilane does not provide water repellency along with its consolidating effect, treated surfaces will be susceptible almoxysilanes weathering influences by absorbing water. Ethyl silicate conaolidation consoUdants have been applied with success in many other sites and countries, as well. As mentioned before, the presence of reactive -OH groups on the mineral grains of the stone can lead to a molecular attachment of the siloxane chains to the mineral grains. The comparison of the treated test area to the adjacent untreated area provides an indication of the treatment’s effectiveness.
The cost also should not be disregarded in selecting the appropriate consolidanL Inthe characteristics of an ideal stone preservative had already been described by Heaton. Preprints of the Contributions to the Paris Congress, September One of the most important properties of alkoxysilanes is their ability to penetrate deeply into porous stone. Alkoxysilane consolidants have a limited service life like other 41 conservation treatments. The number of applications and the waiting time between cycles or applications can vary for different products, therefore each product should be applied in accordance with the manufacturer’s recommendations.
Various proposed tests are still in the development stage and it is not yet certain that they will in alkkoxysilanes provide realistic assessment of the treatment Recently, an ASTM American Society for Testing and Materials committee ASTM Sstone E-6 on Buildings is in the process of establishing a guideline for the selection and use of stone consolidants. Alkxysilanes surface was impregnated with the mixture, first by spraying then by brushing total 5 applications to prevent the breaking away of raised crusts.
Because reattached crusts may be loosened and detached through the application of pack techniques, it seems that only mechanical cleaning is applicable in this case, which is time consuming and not feasible for large surfaces.
Controversy in the publications over the use of alkoxysilanes on stone and adobe aokoxysilanes might partially result from the lack alkoxysilaned research and an incomplete understanding of the complexity of alkoxysilane chemistry.
In addition, the author claims that the adobe’s texture, which is formed of ill-sorted and loosely packed constituent grains of different sizes, accelerated the deterioration.
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Alkoxysilanes are a family of monomeric molecules that have the ability to hydrolize with water to produce either silica or chains of alkylpolysiloxanes. After a certain time period, re-application of the same consolidant or a different one will be required for a consolidztion protection of the masonry substrate. Though research alkoxsilanes new conservation materials has its place, it is only through a complete understanding of traditional materials and technologies and mechanisms of decay that suitable approaches can be developed for a wide variety of issues in conservation.
Despite the poor performance of alkali silicates, these types of stone consolidants have never completely disappeared from the market.
Full text of “Alkoxysilanes consolidation of stone and earthen building materials”
Another drawback reported was that after the vacuum is released, the consolidant tends to migrate inwards resulting in lesser consolidation of the surface than of the inside of the stone. When the solvent conaolidation, the polymer remains in the stone. Elsevier Science Publishers B.
Technical Studies in the Arts, Archeology and Architecture. In conclusion, it is evident that there have been radical changes in the conservation of stone and earthen building materials in the past twenty years and these developments will undoubtedly be subject to further changes in the futiu-e.
Poor penetration is also among the disadvantages of synthetic organic polymers. After treatment, all the raised crusts were reattached to the surface. The physical and chemical nature of the substrate also influence the polymerization process.
Treated and untreated samples are then compared to evaluate the change in the characteristics of the masonry caused by the consolidating treatments.
Alkoxysilanes and the consolidation of stone
On the other hand, if the polymerization is too fast, gelation will occur before an effective penetration is obtained and consolidation will occur only at the surface, creating a potential source of future failurc. You may send this item to up to five recipients. Those hydrocarbon groups are often represented by the letter R. McDonald, ” Coatings, Sealers, Consolidants,” p.
Furthermore, on-site testing indicates the rate of application, rate of consumption and exact application procedures to be used under field conditions, such as the number of applications and how the products are applied.