Since thousands of years, various kinds of adhesives and sealants have been in use. Early hunters may have seen improvement in their aim by bonding feathers to arrows with beeswax, a primitive adhesive form. The Tower of Babel was probably built with mortar and tar or pitch as a sealant. Carvings in Thebes (circa 1300 BC) show a glue pot and brush to bond the veneer to a plank of sycamore. Until recently, most adhesives and sealants evolved from vegetable, animal, or mineral substances. In the early 1900s, synthetic polymeric adhesives began displacing many of these naturally occurring products due to stronger adhesion, greater formulation possibilities, and superior resistance to operating environments.
Presently, there are various types of sealants available in the market: polysulphide sealants, polyurethane sealants, silicone sealants, coal tar and bituminous sealants, and many more. STP Ltd, a subsidiary of the Berger Group, is a company known for developing innovative products. It is among the largest manufacturer of sealants in India.
Movement Accommodation Factor (MAF)
Most of the sealant manufacturers assign a movement accommodation factor (MAF) to each of their products to provide a value for calculating joint dimensions. But so far, there is no universal definition for this factor.
The movement accommodation factor means the total movement range between the maximum compression and the maximum extension that a sealant can accommodate. It is expressed as a % of the minimum design joint width.
Application- Sealing Of The Joints
- Examination of the Joints: The contractor should examine all joints’ joint size and condition and report all technical/practical difficulties that are not acceptable to the main contractors. The joints shall not be wet.
- Cleaning of Joints Faces: The joint faces should be cleaned by wire brush and dust to be removed thoroughly. If there is oil, then it has to be cleaned with xylene or toluene.
- Installation of Back-Up Material and Bond Breaker: The back-up material and bond breaker shall be placed in the joints to allow the placement of the sealant to the desired depth, the surface of which should be recessed by not less than 3 mm below the pavement surface.
- Priming: Apply primer in two coats as recommended by the manufacturers. Avoid brushing on the bond breaker tape. Allow the primer to dry as per the specification.
- Apply the masking tape on the edges of both the joint faces. Tape shall be removed immediately after the tooling.
- Sealant Pouring: Fill the sealant in the ready joint by hand or machine. Use a spatula for filling into joints. Fill some extra material and then do the tooling with a knife blade and pull down the sealant surface level. After tooling, remove the masking tape. The material will self-level.
- Curing of Sealant: Allow the sealant to cure as per the manufacturer’s recommended specification before starting any other operation.
- Cleaning of Tools: Clean the tools and equipment immediately after applying solvents such as xylene or toluene.
Major Sealants Available In The Indian Market
Two-component, polysulphide polymer-based sealants like ShaliSeal® PS PG UV resistant, flexible, tear-resistant, rubbery, self-levelling, pourable, non-staining sealant, which adheres to most of building materials like cementitious substrates, aluminum, glass, wood, mild steel, etc. ShaliSeal® PS PG cures at ambient temperature have excellent recovery characteristics after extended period of compression/elongation with outstanding resistance to most chemicals, weather conditions, aging and shrinkage, and other sealants ShaliSeal® PS PG 30 having Movement Accommodation Factor (MAF) of 30%, for butt joints.
Two-component Polyurethane sealant like ShaliSeal® PU 2K PG is a modified PU, which cures to form a durable, flexible, watertight bond with most building materials and can accommodate dynamic joint movement.
Method Of Application Of Sealants
Ensure that all joints are completely dry and free from all traces of dirt, dust and grease. Clean the surface thoroughly by wire brushing, either hand or machine operated.
Ensure dried and cleaned bonding surface in all joints to be sealed. Preferably, all joints should be parallel and straight for better sealing. Repair spalled joint with ShaliFix EM.
Ensure the depth does not exceed the width; use back-up material to avoid third face adhesion and to avoid contact between forming board and sealant.
Use the primer on the joint’s vertical side faces by ShaliPrime S to ensure strong bonding between substrate and sealant by using a clean, dried brush.
Providing & Pouring ShaliSeal® PU 2K PG (modified two-component polyurethane sealant) into Joint.
Government focus to speed up infrastructure like power, ports, roads, freight corridors, industrial hubs, etc. is the driver for the sealant and adhesive, as well as the construction chemical industry. Due to COVID-19, it will still take some time for the market to pick up. The way India does business will change. The interactions are getting virtual. Apart from this, a strong network of authorized applicators has been trained by the company. To execute the jobs and provide after-sales service, supported by the company team of Engineers and technical operators would be the emerging trends.
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