Adhesion in Tension

In principle, the weakest way to use an adhesive, yet the principle on which many expansion joint and sealant technologies rely for their performance.  Adhesives are best used in shear.  The more durable joint sealing technologies rely either on adhesives in shear as in "membrane/nosing" type products, or use inherent compression to diminish or eliminate adhesion in tension on the bond line as well as within the sealant or adhesive material itself.

Continuity of Seal

The assurance of watertightness in an expansion joint throughout its length and through all changes in plane, direction, and intersection within a single joint sealing technology or between one or more technology types.

Nosing Material

A resin material (usually polyurethane based) with aggregate additives that is mixed and poured in the field on each side of a structural expansion joint gap.  The material when cured is less rigid than the adjacent concrete substrate and as a result is more forgiving of traffic impact and suddenly applied vehicle loads.  A high performance nosing material should be conservatively loaded with aggregates so as to preserve flexibility and avoid brittleness.

Thermal Shock

The rapid opening or closing of an expansion joint gap as the result of abrupt temperature change. The abrupt change causes the rapid shortening or lengthening of the structure on either side of the expansion joint causing a rapid cycle of compression or extension in the joint material. Thermal shock can result from the passage of a fast moving rain storm that rapidly cools a sun-baked structure on a hot summers day.  Can also result from abrupt seasonal temperature changes particularly in spring and fall.  Materials used in sealing structural joints subject to thermal shock must be capable of handling the resulting rapid cycling while remaining bonded to the substrates and while preserving watertightness.