Silicone Masonry Water Repellents

In-plant impregnation of low-fired ceramic products. Low-fired ceramic products such as roof tiles, facing tiles and unglazed floor tiles are made water repellent by immersing them in dilute silicone masonry water repellents thereby preventing efflorescence and imparting water repellency (Wacker-Chemie, 1982). Prefabricated concrete components, plaster of paris and aerated concrete can also be treated in this way. 

Figure 6.17 Exterior walls of a building, impregnated with silicone masonry water repellent. Reproduced with permission from Fosroc...

Wacker Chemie (1983) The Impregnation of Exterior Walls with Silicone Masonry Water Repellents, Wacker-Chemie GmbH, Munich. 

Cakoda. [Calbar] Silicone masonry water repellent. 

Summary 5 Application Areas for Silicone Masonry Water Repellents... 

Silicones have been used as masonry water repellents for more than 40 years. Mineral btiilding materials absorb water and change their properties. The source of water is moisture, frost and efflorescence. The absorption of water depends on the porosity of the material. Water conveys destructive agents inside the building material, causing damage to the building. The absorption of water occurs by a number of routes (Wacker-Chemie, 1989), as will now be described. 

A summary of outstanding advantages, chief limitations, and typical applications of silicones as masonry water repellents follows ... 

Hager (1995), noting that water-based silicone systems had been used on masonry and concrete to provide water repeUency, investigated their potential as wood protection agents. He mentioned the work of E.G. Rochow, who built a house in 1958 using cedar that was treated with a silicone solution as a water repellent. After 28 years, the silicone protective layer was still sound. Hager treated wood with water-based silicone microemulsions and found that good water repellency could be obtained. 

Exemplary water-repellent treatments for masonry surfaces include metal stearates, oils, waxes, acrylates (both polymers and monomers), silicones (solvent-based and emulsion), siliconates, silanes and, fluorochemicals. In contrast, to waterproofing coatings, water-repellent coatings, because they are permeable to water vapor, do not trap moisture and, therefore they can reduce spalling. In addition most water-repellent coatings do not alter the appearance of a porous masonry. 

A substance that, because of its physicochemical nature, will not mix or blend with another substance.. All hydrophobic materials have water-repellent properties due largely to differences in surface tension or electric charges, e.g., oils, fats, waxes, and certain types of plastics. Silicone resin coatings can keep water from penetrating masonry by lining the pores, not by filling them they will not exclude water under pressure. 

Ethyl silicate (tetraethoxysilane) is often used without modification as a water-repellent material for concrete and masonry in general. All, or nearly all. the ethoxyl groups are hydrolyzed by the moisture of the air to form cross-linked watcr-rcpcllcnt polymers. The material is applied in desirable thickness, dissolved in some volatile solvent which soon evaporates. Silicone resins which arc partially condensed before application, or even fully condensed, can also be used here. In the latter case, hardness is achieved on evaporation of the solvent. Certain silicone resins arc useful as hydrophobic agents for the impregnation of paper and fabrics. 

Building materials exposed to weathering are corroded by the action of atmospheric influences, especially water destruction is unavoidable in the long term. Water-repellent treatments can certainly not totally stop these harmful processes, but, given adequate envelopment and attachment to the substrate, nanoscale silicone resin networks can retard material decomposition because of their high durability. Since damage caused by hydrophobic measures can be virtually ruled out if the treatments are properly applied, the organosilicon compounds used in masonry protection will become more and more widely used. 

Silicones are well-known as water repellents. They have been employed on masonry above grade level to repel liquid water not under pressure. They are used above grade level and not under hydrostatic pressure. For instance, they line the masonry pores but do not fill the pores. Thus, they are not a moisture barrier but a moisture repellent. 

The clear-colorless nature of silicone repellents allows preservation of the original appearance of the concrete. Their lack of film formation leaves the masonry pores open, thereby allowing transport of moisture outward to the atmosphere. They are highly durable to environmental conditions and will retain their repellent properties for several years. There are two types of water-repellent silicones (1) one is the resin-solvent type that is characterized as a partially hydrolyzed, partially alcoholized silicone resin dissolved in a hydrocarbon solvent. Generally, such products approach the 5% nonvolatile level. (2) The second is a water-soluble alkaline silicone repellent that is recommended for use on limestone and other nonsiliceous stone and masonry. 

The single largest use of silicone resins is as water repellents for stone and masonry. The resins also find important applications in paints and finishes, especially for high-temperature use, and increasingly as additives to conventional paints. Among the numerous speciality uses which have also been developed, siloxane resins are used to coat pharmaceutical pills and as encapsulants for electronic components. 

Uses Reactive intermediate in the synthesis of silicone-organic copolymers for protective coatings provides a water repellent protective coating for wood, masonry, and metal substrates also for mold release agents, filler treatments (hydrophobic surf.)... 

Chem. Descrip. Reactive silicone polymer sol n. in I PA Uses Water repellent for masonry and wood coatings film-former for mold release coatings surfactant for PVC foam antifog coatings for glass... 

Uses Primer, water repellent, paint adhesion promoter for masonty Features Penetrates deeply into new or existing masonry surfs, to form flat penetrating masonty primer, or clear water repellent low VOC strengthens substrate max. water tepellency will be realized in 72 h Properties Yel. or orange liq. sp.gr. 1.02 flash pt. 67 F ref. index 1.42 VOC 252 g/l 100% silicone content... 

Silicones, water repellent in water R R N N R Used on masonry surfaces. 

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