As mentioned in detail above, sealants are commonly used to fill cracks and openings and seal joints as well as provide a barrier to air, water, moisture, gas, noise, dust and smoke. The building and construction industry, thus, involves numerous applications for sealing compound. The key application areas are discussed below.
Joints in Traditional Masonry
Sealants for Masonry
Masonry may be made with concrete, bricks, concrete blocks, sometimes cellular concrete, according to the construction techniques in favor of each country. Although these materials do not have high coefficients of expansion, the movements of the joints may become high when the parts of the construction (panels, complete walls, high rise structures…) are large.
There are several types of joints in masonry:
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Expansion and shrinkage joints
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Separation joints
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Floor joints in slabs and screeds
Some Typical Uses of Sealants
When a concrete wall or floor has very large dimensions, cracks would appear resulting from shrinking of the concrete after complete drying and expansion resulting from water intake would be also a problem. Thus, it must be split into smaller sections, separated by voids or joints so that the concrete may change in dimensions without adverse effects. These joints must be filled with a suitable sealant.
Sealants for Precast Concrete Panels and Slabs
Prefabricated or precast concrete elements (panels, floor slabs) are installed with void joints between the elements.
These precast concrete elements are not very large: only a few meters width and height, consequently their movements are limited and require only plastic sealants such as butyl, PIB, acrylics.
However, if the building is very large, expansion and shrinkage of each element must be added together so that the total movement may become large, and in this case it will be necessary to use elastomeric sealants such as polyurethanes or MS polymers, which have a very good adhesion to concrete.
Sealants for Precast Concrete Panels and Slabs
Sealants for Joints Related to Curtain Walls
Here, there are many different types of joints:
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Vertical and horizontal joints between sandwich panels or decorative siding panels and the structure, between 2 panels, between sandwich panels and windows. In these cases, the materials are frequently quite different as far as thermal linear expansions are concerned: for instance in joints between glass panels and metal panels.
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Joints between curtain wall and floors (these latter may be of concrete or steel in high rise buildings)
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Joints between metal wall sidings and the structure (which may be steel or concrete)
These joints involve large movements therefore only high performance elastomeric sealants may be used.
Roof Sealants
Roofs, whether flat or inclined, are subjected to rain, snow which may stagnate on the flat roof terraces, therefore the waterproofing must be excellent, and the sealants must be selected according to the climate and the expected movements.
Roof Sealants Requirements
Roofs may be built with different components and materials (tiles, slates, shingles, metal panels, roofing waterproofing materials, gutters, sheds, velux windows, chimneys) that must be sealed together.
- Concrete roof slabs - The joints between roof concrete slabs must be sealed according to the masonry techniques. On top of these slabs there are roofing materials which are also sealed by different techniques:
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Roofing sheets and insulation panels may be bonded and sealed with bitumen or bitumen compositions reinforced by the addition of elastomers,
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Roofing membranes made of PVC, EPDM, hypalon are bonded carefully together with adequate adhesives (rubber-based adhesives, PUR) supplied by the roofing membranes suppliers,
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The whole surface of the terrace may be coated with a thick waterproofing coating, applied by spraying, usually polyurethane coatings.
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Waterproofing between emerging parts and roofs - Emerging parts such as chimneys, sheds, ventilation metal ducts, must be sealed with plastic or elastomeric sealants. Polyurethanes and MS polymers, which display excellent adhesion to many materials, are the best choice.
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Waterproofing and sealing of corrugated roof panels - Here 2 types of products may be used:
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Butyl or PIB preformed tapes, which must be compressed between the panel edges,
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Acrylic or butyl sealants: applied from cartridges in thick diameters (8 mm) the sealant bead is compressed during the installation between the 2 panels.
Sealants Used for Structural Glazing
In structural glazing, glass panels are attached strongly and durably to the metal structure of the facades of buildings. The wind load and the weight of the glass panels are transferred to the metal structure through the adhesive/sealant, which is always a silicone product. This is a very demanding application because the whole system depends on the adhesion and the internal cohesion of the adhesive/sealant, and there is a risk if the glass panel would fall from a high level.
For this reason, the bond between the glass panels and their metal frames is made in the factory in order to control carefully all parameters: cleaning of surfaces before bonding, application of the silicone product, quality controls and adhesion and durability tests.
Moreover, some mechanical fasteners are added in order to provide additional safety.
First, the designer must calculate all the stresses that will occur in the joints:
- Stresses due to the wind pressure and depression,
- Weight of the glass panels: their weight must be borne by some mechanical attachments (such as clips, shims or spacers) because the silicone adhesive/sealant is not supposed to bear this permanent load,
- Movements of the joints: the general movements of the structure must be absorbed by the metallic connections between the structure and the frames of the glass panels. The only admissible movements are those which result from the differential expansion and contraction of the glass and the metal frames. These movements will cause a shear of the adhesive/sealant.
Starting from the calculated maximum movement, the designer will select the type of sealant and its movement capability and then calculate the thickness of the structural joint (between glass and frame).
Window Glazing Sealants
This is the largest use of sealants if we include the sealing of double or triple insulated windows. The various sealing operations are to be performed for the complete installation of glass and windows.
Insulated Double or Triple Glass Windows
As far as sealing is concerned, insulated glass units are double sealed (refer to figure above).
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The inner sealant is mainly polyisobutylene (PIB) or butyl sealant because these products have a very low permeability to water vapor or moisture vapor transmission (MVT): for instance, the permeability to water vapor of PIB sealants JS 780 and JS 680 from TREMCO. Is less than .02 g/m2/hour for a 2 mm thickness, measured according to the European standard EN 1279-4C.
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The other sealants are not acceptable in this respect, for instance, the MVT of polysulfides or polyurethanes ranges from 2 to 6 g/m2/day, and for silicones it ranges from 10 to 20 g/m2/day,
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The outer sealant is an elastomeric sealant which functions both as an adhesive bonding the 2 glass panels and a sealant against water, air and insects. This sealant may be based on polysulphide, polyurethanes, silicones or hot melts.
Insulated Double Glass Panel
Window frames are inserted into the main frame of the building and this requires a good sealing between the window frame, made of wood or metal or PVC, and the main frame which may be masonry (concrete, bricks or curtain walls, or sometimes, in Nordic countries and USA, wood frames).
Many different sealants may be used for that: elastomeric PUR, plastic acrylics sealants (water based or solvent based), butyl sealants and also PU foams. The differential movements are not so important because usually the windows dimensions are limited (1 to 3 meters, no more) and do not require elastomeric sealants.
The designer or the contractor should design the joint width according to the expected movements of both the main frame and the window or door frames.
Ceramic Tiles and Sanitary Ware Sealants
This is a simple and well-known application: joints between 2 tiles are usually made with cement-based grouts, but when it is necessary to seal the joint between 2 large tiled areas the sealant must be flexible enough in order to accommodate larger movements.
In bathrooms, showers, kitchens, swimming pools, etc. there is high humidity and water spilled over the floors and walls and it is mandatory to seal the tiled surface against penetration of the water into the walls and floors and then into the next rooms. This may be done by using a waterproof tile adhesive or a waterproofing coating or membrane, but anyway a waterproof joint between the tiles is also very useful.
Ceramic Tiles and Sanitaryware Sealants
Also the expansion coefficient of ceramic tiles being low, when there is a very large tiled surface (larger than 10 m2 for instance), this surface acts as a monolithic surface, and at the joint between 2 tiled sections there might be some movements, for instance, when the wall or partition is made of particle boards or plasterboard which have a larger expansion with humidity. Some cracks may then occur at the joint on drying and therefore the joints must be filled with an elastomeric sealant which will forbid water to penetrate these cracks and joints.
ln this case, silicone sealants are the best choice because they combine high water resistance, tolerance to large movements, long term durability, they may be formulated with many different colors that can match the tiles and sanitaryware colors, their colors do not change with time, and they are easy to apply even by nonprofessional users.
However, the silicone sealant should resist mold growth which may become fast due to the use of hot water in bathrooms. Some grades are formulated with anti-mold growth compounds for this use.
Sealants for Civil Engineering Works
In civil engineering, some parts of the construction may be quite large, for instance, segments of concrete bridges, dams, or even road or airports concrete slabs which may reach 10 meters in length.
Therefore, the expected movements may be also large and thus, civil engineering contractors use sealants which are different from those used in Building, because the width and section of joints here are higher. They prefer the following sealants types:
Rubber-modified Asphalt and Bitumen Sealants
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A rubber-modified asphalt sealants are cheap.
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These products are hot poured at temperatures from 150 to 200°C.
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These mastics start to creep at 40°C.
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85% of all roads and airport runways are still jointed with rubber-modified asphalt.
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They must meet American specifications ASTM D 3405 and federal specs SS-S 1401 B.
Tar - PU Compounds
- These are PU sealants to which the manufacturer adds tar in order to lower its cost.
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These have good performances and relatively cheaper price which is quite acceptable.
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They have a good resistance to kerosene and to the hot air exhaust of jet aircraft so that they may be used for airports runways even at the start of the runway where the pilot tries the full blast of the motors.
PVC Plastisol - Tar
Hot poured at 150°C, more expensive than the rubber modified asphalt but higher performances (resist to kerosene but not to hot jet exhaust, withstand 10 to 15% elongation), they meet American specification SS-S 1614, and in the USA they have 5% of the civil engineering market and are used for airports runways, roads and buses terminals.
Silicones
One component silicones have only 5% of the market, they are used for airport runways and some bridges, when the customer require high performances such as low modulus, high elongation, long term durability. 2 component silicones are seldom used.
Note: In some cases, contractors may be wrong in using a cheap sealant because it will need a much larger joint and, because the cost of application is the same, high performance sealants may turn out to be quite competitive with the cheap ones or even cheaper for the total cost.
Elastomeric Rubber Profiles and Preformed Seals
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These are used when the joint width is very large: 2 to 10 cm, (for instance for large bridges, reservoir dams…) and when the 2 sides of the joint are perfectly parallel and flat.
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They are compressed between the 2 lips of the joint so that their width should be approximately double the average width of the joint.
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They are usually quite expensive for instance 10 euros per linear meter for a 5 cm width.
Epoxy Bonding and Sealing Products
These are not really sealants but rigid adhesives which bond and seal the concrete to concrete joints, such as for instance in the segmental bridges where concrete hollow segments are bonded and sealed together with epoxy adhesives, or epoxy resins used for repair of cracks by injection.