Revisions log for Answer #1417

To protect porous building materials from external moisture, reduce water permeability and wetting by water, they are impregnated with special chemical compositions (hydrophobisers). This method of treating the surface of building materials is called hydrophobization.

It is used to protect fragile and quite porous materials, such as gypsum and aerated concrete, as well as quite hard and dense materials, such as concrete or natural stone in basements, foundations, facades, walls, tunnels, etc.

Porous mineral materials (with a porous structure) that are used for building structures are negatively, even aggressively, affected by moisture from the surrounding area (rain, fog, snow, meltwater, groundwater...). As a result of such impact we sometimes observe salt stains on brick walls, destroyed (peeling) foundations, faded marble with typical whitish stains, torn off peeling plaster or facade cladding.

Hydrophobization sharply reduces the water absorption of the treated surface.

The process consists in applying acrylic-based or, less frequently, silicone-based compositions to porous surfaces in order to impregnate them. Depending on the porosity of the material, the impregnation depth can vary from a few millimeters to several centimeters. As a result, the treated material becomes water-repellent and its frost resistance increases.

During application of protective compositions, in capillaries and pores of porous material a chemical reaction occurs which forms insoluble crystals, blocking access of moisture inside the material. At the same time the crystals allow air in – the treated material "breathes".

The main properties that material treated with hydrophobics acquires: water-repellent properties, protection against "efflorescence",  increase of heat-insulating properties, because the material stays dry all the time, increase of frost resistance, prolongation of service life of finishing materials applied to treated surfaces. Microorganisms do not develop on the surface, the material does not succumb to erosion. The durability of the material and the whole structure increases. Consumption of paint and varnish materials decreases.

The treated materials retain these characteristics for about 10 years. If hydrophobisers are added to the mixture during the manufacture of building materials, hydrophobic properties are retained throughout the life of the material.