Sealants are widely used in a variety of industrial, commercial, and residential applications. Applications range from low-end, unspecified uses, such as crack filling in driveways, to high-end, specified, and regulated uses, such as structural glazing. Construction sealants are utilized in a multitude of applications, for example, in glazing and perimeter joints on windows and doors; roofing terminations; perimeter joints in bathroom and kitchen appliances; weather-sealing joints in facades and curtain walls; expansion joints in airport runways, highways, bridges, plazas, and parking decks; joints in water and wastewater treatment facilities (including submerged environments); and in fire-stop sealing of joints and penetrations in public facilities (fire partition wall sealing), such as in hospitals, schools, or power plants. Due to the wide use of construction sealants, the global market for these materials now exceeds 800,000 tons in volume and $3 billion in sales value.
Construction sealants can be categorized by form, ability to cure or harden, chemical binder, performance, or end-use market. The major distinction in product form is between preformed sealants (gaskets and strips) and in situ cured or hardened (wet-applied) sealants. This chapter focuses primarily on in situ cured sealants, and much of the detailed discussion is limited to the modern high-performance elastic sealant types. In situ cured sealants are applied to a joint in paste-like or liquid form, and they harden or cure in place. Similar to adhesives, in situ cured sealants rely on their adhesion properties to maintain a durable seal and perform their function. However, in situ cured sealant formulations typically possess higher elasticity and flexibility than adhesives and generally display lower cohesive strength. Some sealants, termed structural sealants, are used in the same manner as adhesives to transfer loads between building components; however, these sealants still maintain a higher level of movement capability than conventional adhesives.