ASTM D8 - Standard Terminology Relating to Materials for Roads and Pavements

Asphalt rubber is defined as a "blend of asphalt cement, reclaimed tire rubber and certain additives in which the rubber component is at least 15% by weight of the total blend and has reacted in the hot asphalt cement sufficiently to cause swelling of the rubber particles." 

ASTM D 6114 - Standard Specification of Asphalt Rubber Binder

Defines asphalt rubber binders as "a blend of paving grade asphalt cements, ground recycled tire rubber and other additives, as needed, for use  as binder in pavement construction. The rubber shall be blended and interacted in the hot asphalt cement sufficiently to cause swelling of the rubber particles prior to use."

Wet Process - High Viscosity

Method of modifying asphalt binder with crumb rubber modifier (crm) before incorporating the binder into the asphalt paving materials. The wet process requires thorough mixing of the crumb in hot asphalt cement and holding the resulting blend at elevated temperatures for a designated minimum period of time to permit the interaction between the CRM and asphalt.

  • Most widely used in CA, AZ, FL & TX
  • Contains 18-22% crumb rubber
  • Particle sizes #8 to #10 top size
  • Throughly mix CRM and other components with hot (375-425 F) asphalt cement
  • Interact at 350-375F for designated period (typical minimums 45-60 minutes)
  • CRM particles swell, exchange oils with asphalt cement
  • Rotational viscosity is discriminator for appropriate use

Specifications vary by agencies, the above outline is for general information only.

The wet process has been in use since the 1960's.

Rubberized hot mix asphalt applications are most effective as surface courses. Gap graded and open graded mixes made with high viscosity asphalt rubber binder are typical.

Rubberized hot mix asphalt can be produced using warm mix additives.

Rubberized Asphalt