All materials have a surface energy. It is a measure of how much a liquid or solid wants to stick together. A liquid with a low surface energy e.g. oil, is able to "wet" a material with a high surface energy e.g. stone. Dry-Treat sealers work by changing the surface energy at the surface of the building material so that it becomes lower than that of the liquid trying to wet it. That means that contaminating liquids such as oil and water are no longer attracted to that surface and are repelled. This is achieved by means of a semi-permanent chemical reaction between the sealer and the atoms of the building materials.
At the heart of a Dry-Treat impregnating sealers are specially engineered molecules - modified silane and fluorine polymers which penetrate much deeper and bond permanently inside the treated material by chemical reaction.
This innovative and different technology gives Dry-Treat impregnating sealers their superior properties and unique benefits, including a lifespan many times longer than other sealers. The main molecules have two main parts with quite different properties. Part of the molecule is hydrophobic and/or oleophobic i.e. repels water and oil, while the other is hydrophilic and so attracted to water.
When the sealer is applied to the surface of porous building materials it immediately starts to react with moisture in the air and in the material. This reaction causes the part of the sealer molecules which is attracted to water to break off leaving a changed molecule behind, which is able to react with the surface layers of the masonry. In the next stage of the reaction process, this changed molecule breaks the bonds between the masonry and attached oxygen and hydrogen atoms and bonds directly to the lattice in their place. Unlike surface coatings that rely on weak hydrogen bonding or mechanical holding, this chemical bond is as strong as the bonds holding the masonry together. In fact these special molecules become part of the material itself, without affecting its look, slip resistance or breathe-ability. This bond causes the contact angle between water and masonry to change. It no longer acts like a 'hard sponge' which absorbs liquids, but repels liquids instead.
Salts must be in water to move through a porous building material via capillary suction. Ions in salt water are surrounded by a shell of water molecules. These hydrated ions are too large to pass through the water repellent barrier caused by the Dry-Treat sealer i.e. the building material will repel the water and the dissolved salts - in particular the very damaging chloride ions. Freeze-thaw is a phenomena that occurs when water fills up the surface pores of a porous material. When that water freezes due to below zero temperatures the water expands and may spall the surface. A sealer than can provide resistance to salt attack is also an excellent indication that it will protect a building material from freeze-thaw attack.
Depth of impregnation
A good depth of impregnation gives the Dry-Treat sealer protection from weathering and traffic. It also can stop unsightly efflorescence salts reaching the surface of the building material. The uniform depth of penetration of the treatment can be measured relatively easily by breaking a sample piece of treated material that has had time to cure and measuring the "dry" section depth from the surface after it has been soaked in a water-based dye for a few minutes. The depth of penetration achieved will vary with the surface absorption and amount of product applied. The more product applied will result in a deeper depth of impregnation.
In addition, Dry-Treat sealers contain a relatively slow moving reacting liquid, with a viscosity similar to that of water. This means that even on slightly moist building materials over time it can displace the water and penetrate deep into the material. This is quite useful for the treatment of those parts of a marine structure that are in the tidal zone.
Cement based materials are highly alkaline due to the presence of calcium hydroxide i.e. they have a high pH. Unlike many other products the chemical bond of a Dry-Treat sealers can withstand strong alkali attack from calcium hydroxide. The Alberta Transport & Utilities have developed a test to determine the ability of a sealing treatment to withstand alkali attack and that test has become the basis for similar performance based sealing specifications around the world. Their test involves soaking a treated sample of concrete in 0.1 molar solution of potassium hydroxide, which has a very high pH, for 21 days then testing the sample for water up-take. To date, the best performing material has been the Dry-Treat type of sealer.
The Dry-Treat sealer attaches itself to the building material molecular lattice where it is able to repel liquids such as water. Dry-Treat's special liquid-repelling sealing molecules are thousands of times smaller than the molecules in standard silicone resin or fluoro-polymer type impregnators, and they won't block the pores, so surfaces treated with Dry-Treat's impregnators retain maximum breathe-ability after treatment. In short - water (and /or oil) are repelled, but water vapour is able to evaporate out. The reason for this phenomenon is related to hydrogen bonding i.e. the water molecules stick together as a liquid and are subsequently resisted by the sealer. Water vapour does not stick together and travels alone and is able to by-pass the treatment. This means that trapped moisture in the material can evaporate over time and dry out the substrata.