What are the Different Types of Joint Sealant?

Paul Scott

Joint sealants are typically fluid, gel, or solid agents used to seal construction gaps in masonry, asphalt, timber, or steel structures. The use of a joint sealant serves the dual purpose of creating a physical barrier to exclude water, air, or dirt while creating an aesthetically pleasing finish to otherwise unsightly joints. The two most common types of joint sealant are fluid/gel and preformed solid seals. These joint sealants are specifically engineered with specific physical attributes and may also have additives such as flame or bacterial retardants included in their formulations.

Silicone sealant, a type of joint sealant.
Silicone sealant, a type of joint sealant.

Joints in construction elements are an unavoidable and often essential feature of most industries. Whatever their function, most joints require sealing to keep out moisture or air and exclude plant and dirt intrusion. In the case of decorative structures such as walkways, patios, decks, and pool paving, the joint sealant should also make for a visually pleasing finish. Joints in high traffic or stress applications such as sidewalks, roads, and bridges need to exhibit superior abrasion and shock resistant qualities along with their general sealing characteristics.

Applying silicone sealant to a joint.
Applying silicone sealant to a joint.

There are two main families of joint sealant: fluid or gel sealants and preformed products. Gel and fluid sealants include a wide variety of latex, silicone, polyurethane, polysulfide, and acrylic products which are generally poured into the joint or applied with a caulking gun. These sealants exhibit excellent elasticity, weathering, and tear-resistant qualities and in many cases may be tinted or painted to match the surrounding structure. Fluid sealants are available in many special grades which include mold and mildew resistant products for bathrooms or kitchens and chemical grades which are fuel or acid resistant. These sealants are the most commonly used products for domestic and do-it-yourself (DIY) applications to seal joints in paving, decks, and concrete slabs.

Preformed joint sealants are usually available as previously cut strips or as continuous lengths on rolls and include wood, rubber, foam, fiber or cork materials. These sealants are most commonly used to seal joints in glass panes, metal panels, automotive parts, plumbing fittings and shop fitted furnishings. Many of the cellular rubber and foam products are fitted under compression which requires specialist application tools. Sealants such as wooden strips make for attractive and durable exterior seals for walkways and driveways. Natural fibers such as hemp are used to seal joints in plumbing installations, particularly those involving hot water. Fiber and cork sealants are most commonly used to manufacture gaskets for use in automotive, gas, and high pressure water systems.

Joint sealants are generally designed for specific joint types. Physical properties such as tear strength, elasticity, fatigue, and abrasion resistance need to be matched to the sealants intended use. This is also true of environmental elements in an application environment which require additives that are ultraviolet (UV), acid, mildew, and fire resistant. Application-specific characteristics are also important features of the different types of joint sealant. These include application methods, tube or pot life, tack free, and tooling times and application temperatures.

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