Evolution of Extruded Expansion Joint Seals

Evolution of extruded expansion joint seals1. Compression Seal

Description:

  • Multi-cell Neoprene extrusion installed into epoxy “lubricating adhesive” applied to joint face.

Advantages:

  • Best technology available at its introduction shortly after World War II
  • Predecessor of all modern extruded expansion joint seals

Limitations:

  • Anchoring system reliant on adhesive in tension – weakest way to use adhesive
  • Must be force-compressed (squeezed) in the joint
  • Limited movement: Max. joint size limited by relaxed width of seal. Min joint size limited by complex internal webbing.
  • Compression set: permanent loss of ability to exert backpressure against substrate – substrate pulls away from seal
  • Rigid “box” structure combined with poor anchoring system cannot handle vertical differential deflection (up and down) movement.
  • Neoprene thermoplastic rubber extrusion cannot be heat-welded. Terminations and transitions in plane and direction as well as repairs must be glued. Glue dries out over time.

2. Inflated Seal

Description:

  • Double or single barrier Neoprene thermoset rubber extrusion with joint face-applied epoxy “adhesive-in-tension” anchoring system
  • Seal is inflated during installation to improve bond.

Evolutionary Advantages:

  • Reduced interior webbing offers increased movement range over compression seal

Disadvantages:

  • Anchoring system reliant on adhesive in tension – the weakest way to use adhesive.
  • Approx. 18 square inches of adhesive in tension per foot of joint.
  • Bond line stressed by: peeling action during up and down vertical deflection; gravel and sand forced by tires into epoxy-to-seal interface; and standard tension from lateral movement
  • Does not protect joint edge. Blockouts with elastomeric header required to waterproof joint edges and prevent cracking and spalling
  • Durable terminations, transitions and repairs difficult. Neoprene thermoset rubber extrusion cannot be heat-welded. Terminations and transitions in plane and direction as well as repairs must be glued. Glue is not UV stable and dries out over time.
  • Poor extrusion tolerances of Neoprene yields excessive bulk at flexural nodes in gland, inhibiting movement and excessively stressing epoxy bond.
  • Dependent on extremely smooth joint face. Relies on epoxy to fill irregularities.

3. Multi-Cell Blockout Adhered

Description

  • Blockout-anchored multi-cell extrusion with integral punched flanges encapsulated in elastomeric concrete nosing material.

Evolutionary Advantages:

  • Superior anchoring system to compression seal and inflated seal.
  • Elastomeric concrete nosing encapsulates punched flanges, mechanically anchoring seal using adhesive in shear – strongest way to use adhesive.
  • Over 45 square inches of adhesive in shear per foot of seal.
  • Not affected by minor irregularities in joint face.

Disadvantages:

  • Limited movement. Max. joint size limited by relaxed width of seal. Min joint size limited by complex interior webbing.
  • Rigid “box” structure inhibits vertical differential deflection (up and down) movement capabilities.
  • When retrofitting joint-face adhered technologies, requires cutting of blockouts. In new construction, blockouts can be formed.

4. Double Barrier Blockout Adhered

Description

  • Double-Barrier Santoprene thermoplastic rubber extrusion with integral punched flanges encapsulated in elastomeric concrete nosing material.

Evolutionary Advantages:

  • Latest evolution of gland design. Combines high-movement of double barrier inflated seal with integral flanges for secure blockout mounting.
  • Elastomeric concrete nosing encapsulates punched flanges, mechanically anchoring seal using adhesive in shear – the strongest way to use adhesive.
  • Weldabilty of thermoplastic-rubber extrusion allows for continuity of seal through changes in plane and direction and offers repairability.
  • Over 45 square inches of adhesive in shear per foot of seal.
  • Not affected by minor irregularities in joint face.

Disadvantages:

  • When retrofitting joint-face adhered technologies, requires cutting of blockouts. In new construction, blockouts can be formed.