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.

Blockout

A blockout is a condition present at a joint gap edge to accept different types of expansion joint profiles. Also referred to by regional terminology such as knockout, cutout, and others.  (see illustration)

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.

Refers to the attachment of an expansion joint system to the joint faces or substrates to be sealed without the use of any fasteners that are required to be screwed into or embedded in the substrate. 

Non-invasive anchoring on EMSEAL's joint systems is eliminated in favor of the use of the mechanical backpressure of precompressed, foam combined with a pressure-sensitive adhesive impregnation and in some case a field application of a high-bond epoxy adhesive.  The result is that the substrates are not violated be they window mullions, bricks, masonry, historic materials, or even jumbotrons or other sensitive equipment.

Screws and expansion anchors are commonly used to fasten rails, plates, and other systems offered for expansion joint sealing and bridging.  By nature, screws are either self-tapping or require holes to be drilled and then the screws tapped into the holes.  On brittle substrates like concrete, masonry or brick, drilling often results in spalling of the substrates and improper grip.  Usually installed at an angle to the face of the joint substrate the act of screwing is often imprecise resulting in further substrate damage, shearing of the fasteners and loose attachment of the joint system.  At inside corner applications common in additions or building plane changes, it is impossible to position a drill or driver to install anchors in the substrate opposite the inside corner.  This often-overlooked condition results in the joint system being installed into an unreliable adhesive or not anchored at all.

In window or curtain wall mullions, screws violate the mullions and can compromise the waterproofing principles inherent in the mullion design.  In any substrate metal fasteners introduce thermal bridges and thermal breaks that lower or compromise the insulation value of the wall.  EMSEAL systems for wall expansion joints that feature non-invasive anchoring include: SEISMIC COLORSEAL, COLORSEAL, and SEISMIC COLORSEAL-DS

In horizontal plane deck applications, anchors into concrete to secure cover plates are rapidly deteriorated by impact shocks of traffic.  They are also stressed by differential vertical deflection across expansion joints as the result of transient traffic loads.  Finally, anchors into the edges of concrete decks can induce a fault-line of pressure that weakens the concrete's strength and can result in spalling of the joint edge.  EMSEAL systems for deck expansion joints that feature non-invasive anchoring include:  SJS SYSTEM, SJS-HD, DSM SYSTEM, and HORIZONTAL COLORSEAL.

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.