Sealants

  • Sealants are wet-applied materials formulated to both solidify (cure) in-situ and adhere to the joint surfaces in a controlled manner. [1]
  • Sealants must always be treated as a system, as additional products are essential for effective performance – back-up materials, bond breakers and (where recommended) primers or surface conditioners. [1]
  • A material placed in a joint opening generally for the purpose of weatherproofing a building, so designed to prevent the passage of moisture, air, dust and heat through all joints and seams in the structure.[2]
Sealants
Purpose: To prevent the passage of air, water and heat through the joints and seams / to waterproof and to accommodate the continuing changes in the joint movement
Effectiveness of sealant:

  1. Type of sealants used must be able to seal the opening
  2. Joint design
  3. Workmanship
Constituents:

  • Base polymer (to bind the total system and provide its elasticity and durability) Sealants are classified based on the base polymer
  • Fillers (to lower the cost of production)
  • Minor ingredients (eg pigments- to give colour/ solvent – to improve the applicability)
Specific gravity —- 1.04 + -0.03
Hardness – shore A scale —- 25 ASTM D – 2240
Tensile strength —- 1.7 Mpa
Elongation at break -% —- 400 ASTM D – 412
Movement Capability in service —- +25%

Mastic

  • A thick, pasty coating or sealant.[2]
  • They are sealants that simply never cure. [3]
  • One of a variety of quick drying, pasty cement for use when gluing tiles to a wall. [4]
  • Adhesive consisting of asphalt and non drying oil. This type of adhesive must be heated to use.
  • Construction adhesive, which is usually applied from a caulking gun.

References

  1. S.R. Ledbetter, S. Hurley and A Sheehan (1998), Sealant joints in the external envelope of buildings, A Guide to design, specification and construction, Construction Industry Research and Information Association Report 178, Construction Industry Research and Information Association,
  2. Julian R. Panek and John Philip Cook (1991), Construction Sealants and Adhesives, John Wiley & Sons, Inc.
  3. Jerome M. Klosowski (1989), Sealants in Construction, Marcel Dekker Inc New York, TP 988 Klo
  4. www.homeglossary.com
  5. ASTM D2240-02b Standard Test Method for Rubber Property—Durometer Hardness
  6. ASTM D412-98a(2002)e1 Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomer —Tension