Seal-N-Save Systems sealers work by the modification of the surface of the building material and by changing its absorption characteristics. This is achieved by a chemical reaction. You may recall the school experiment when you placed a small needle on a still water surface to see how a film supported it. These same forces cause a raindrop to form into a sphere as it falls through the air and the water pulls towards itself. This film is caused by the surface energy that binds the water together. This intermolecular force is the result of hydrogen bonding and Van Der Waals forces.
Capillary attraction is caused by this surface tension and by the relative value of adhesion between the liquid and solid and to the cohesion of the liquid. A liquid that wets the solid has a greater adhesion than cohesion. Metals for example have a high surface energy ranging from 0.5 to 5 joules sq.m. whereas water has a value of 0.07 j sq.m. and oil about 0.02 j sq.m. A material with a low surface energy will wet a material with a higher surface energy. Both oil and water will wet metal. Oil will spread on water but water won’t spread on oil. Most of Seal-N-Save Systems products work by modifying the natural surface energy of the porous building material by means of a chemical reaction which changes the surface energy, with the result that they repel water, salts and oils.
One of the main active components of our sealers is a molecule that is about 10A in size – good quality concrete pores size is typically 50 to 200A. The molecule consists of silicon, carbon, hydrogen and oxygen atoms. The molecule has two main parts with quite different properties. Part of the molecule is hydrophobic i.e. it repels water.
This other part is hydrophilic i.e. it is attracted to water. When the sealer is sprayed onto the surface of porous building materials it immediately starts to react with moisture in the air and in the material. This causes the molecules in the sealer i.e. the hydrophilic part to react and break off to form an alcohol – in this case ethanol. A new compound is formed called silanol that is able to react with the surface layers of the masonry. The structure of the majority of masonry essentially consists of silicon, oxygen and at boundary layers oxygen and hydrogen atoms. The silanol molecule is very reactive and is able to break the oxygen-hydrogen bond. It then attaches itself to the masonry lattice. Unlike surface coatings that rely on only Van Der Waal forces of attraction or mechanical holding, this bond is very strong and of the same magnitude as the bonds holding the masonry together.
The attachment of the alkyl molecule to the silica lattice causes the contact angle between water and masonry to change. It no longer acts like a “hard sponge” but is able to repel liquids. This phenomenon can be expressed by the equation:
Capillary rise H= 2 x surface tension of liquid x contact angle of the concrete capillary radius x density of liquid x gravity.
Before the treatment the porous building material had a contact angle approaching zero. i.e. Cos (0 degrees) = 1, giving a positive value for H. After the treatment the sealer molecule on the silica lattice causes the contact angle to become about 110 degrees. i.e. Cos (110 degrees) = -0.2, giving a negative value for H.
By definition salt ions must be in water to migrate into the building material through capillary suction. Due to the presence of the seal the building material now repels the water and it also repels the chloride ion.
So, the question you may ask is – how well does the sealer treatment work in protecting the building material against water and salt ingress? Hundreds of independent tests from around the world have verified these properties.
The 244 Report; This paper was produced by the US Transport Research Board who tested over 259 different materials for the protection of concrete. Silane was considered the best all-round material. RTA CTI Report; This report showed that the water up-take was reduced by 98% and the chloride up-take by 97%. It interesting to compare this with some additives that only reduces the chloride uptake by only 30%. Mahaffey Consultants also did some work on the effect of treatment of concrete and found it made concrete about 100 x more resistant to chloride ion ingress. Typically, using silica fume will make the concrete only 10 x more resistant. CTI also found in another report that silane protection was equal to an extra 100 mm (4 in.) of concrete cover over the steel. This is useful for pre-casters who use our products to up-grade the durability characteristics of members incorrectly cast.
Depth of Impregnation
The uniform depth of penetration of the treatment can be measured from the surface after it has been soaked in a water-based dye. Our sealers have a relatively slow moving reacting liquid, with a viscosity less than water. This means that even on slightly moist building materials it can still penetrate deep into the material. This is quite useful for marine structures. A deep depth of penetration is vital to protect the treatment against the effects of weathering and ultraviolet radiation. Just on this subject, it commonly observed that for a few months after treatment the masonry shows excellent water repellency beading. This effect later disappears.
The effect is caused by excess product polymerizing on the surface to produce a greasy silicon type film. This film breaks down in the sunlight. The real work continues to be done below the surface. So, we now have the pores in the first 4 to 10 mm of the material with a repellent molecule attached. The repellent action is caused by the net electron charge of the sealer, which like water is negative.
Also, unlike many other products the bond of this sealer can withstand strong alkali attack from calcium hydroxide. Alberta Transport & Utilities have developed a test to determine the ability of a treatment to withstand alkali attachment and is the basis for similar performance based specifications around the world. Their test involved soaking a treated sample of concrete in 0.1 molar solution of potassium hydroxide for 21 days then testing the sample for water up-take. To date, the best performing material has been our type of sealer.
As mentioned before, the sealer has attached itself to the building material lattice where it acts as a repellant. At the same time the sealer permits the passage of water vapor, so that the concrete can breathe. The reason for this phenomenon is hydrogen bonding. In liquid water, which means that the water molecules stick together and are subsequently resisted by the sealer. Water vapor travels alone and is able to by-pass the silane. This means that trapped moisture in the material can evaporate over time and dry out the substrata.