This document discusses curtain wall construction and sealants. It introduces how curtain wall construction arose in the 1950s using a skeleton structure wrapped with a non-bearing envelope. This allowed for more flexible design using materials like glass, metal, and concrete panels. It then discusses how new elastomeric sealants were introduced to accommodate the greater movement in curtain wall joints compared to older buildings. The document outlines the functions, applications, types, advantages and disadvantages of construction sealants.

1. INTRODUCTION
• The Early 1950s saw the application of the new concept of curtain-wall
construction in high-rise structures through out the world.
• This concept was based on the use of a skeleton of steel or concrete that
was
then wrapped in a separate envelope or non bearing curtain wall.
• This reduced the use of the low-rise bearing wall type construction and
introduced greater flexibility in design through the use of precast concrete
panels, glass or metal panels, unit masonry, and combinations of these
materials.
• Construction was also become much faster, also these
structure are inherently more flexible than bearing-wall
construction, but present new problems is weather
proofing.
Sealents

2. The introduction of the curtain wall was
accompanied by the introduction of
elastomeric sealants that would adhere to
the various surfaces and take
greater movement than had existed in the
older expansion joints.
• The old oil-based caulking compounds
no longer qualified, and the new
materials became “SEALANTS” rather than
caulks.
• However, the term “SEALANT” has been
too broadly used and now
includes a wide assortment of weather
proofing joint materials.
• Sealants or caulking compounds include
viscous liquids, pastes, tapes,
gaskets, and even water proofing
membranes.
• The materials can either cure to a
rubber or remain in a mastic stage.

3. Functions
• Sealants, despite not having great strength, convey a number of
properties. They seal top structures to the substrate, and are particularly
effective in waterproofing processes by keeping moisture out (or in) the
components in which they are used.
• They can provide thermal and acoustical insulation, and may serve as
fire barriers.
• They may have electrical properties, as well. Sealants can also be used
for simple smoothing or filling.
• They are often called upon to perform several of these functions at
once.
• A corking sealant has three basic functions: It fills a gap between two or
more substrates; it forms a barrier through the physical properties of the
sealant itself and by adhesion to the substrate; and, it maintains sealing
properties for the expected lifetime, service conditions, and
environments.
• The sealant performs these functions by way of correct formulation to
achieve specific application and performance properties.

5. Applications
• Horizontal and vertical metal-to-metal and
masonry-to-masonry expansion
and control joints
• Dissimilar material joints, such as metal-to-
masonry or concrete-to-wood
• Joints between precast concrete façade panels
• Spandrels
• Perimeter of doors and fixed window frames
• Exposed exterior masonry control joints
• Expansion or control joints in curtain wall
• Joints in exterior walls
• Concealed masonry-to-floor structure joints
• Repair of larger cracks

7. Types of Construction Sealants
• Silicone Sealants
• Epoxy
• Hybrid Polyurethanes Sealants
• Polyurethanes Sealants
• Elastic Sealants
• Varnish
• Acrylic Latex Sealants
• Bituminous Sealants
• Synthetic Rubber Sealants
• Thermoplastics Sealants
• Butyl Sealants
• Hot Wax
• Proof Sealants
• Polysulfide Sealants

9. Advantages
• Improves Product Durability and Reliability.
• Increases Product Performance.
• Increases Design Flexibility.
• Increases Product Quality.
• Enhances Product Aesthetics.
• Improves Process Productivity and Reduced Manufacturing
Costs.
• Increases weathering characteristics.

10. Disadvantages
Deterioration of sealants causes due to prolonged exposure to water,
ultraviolet light,
and freeze-thaw cycles.
• Loss of Adhesion caused by the presence of coatings or contaminants
that prevent proper adhesion.
• Cohesive failure due to deterioration of the internal integrity of the
sealant; cracking parallel to the interface of the joint is an indication of
this type of failure.
• Inappropriate Choice of Sealant and Improper Joint Design may fail the
joint and losses the adhesion.
• Uncured Sealant that is uncured is often due to incomplete or improper
mixing of the sealant components, or from using materials that have
outlived their shelf life losses the adhesion and fails the joints.
• Bubbling and Blistering of the Surface losses the adhesion and fails the
joints.