ASPHALT RUBBER: TECHNICAL BRIEFING
 
Asphalt rubber, sometimes called rubber modified asphalt or rubber modified bitumen is a blend of crumb tyre rubber, extender oils and asphalt (bitumen). The rubber content should be, for optimal performance 18-22%. In some cases other polymer sources or natural rubber waste may be added for specific property enhancement.

In the late 60's Arizona Department of Transportation became interested in improving their pavements using modified asphalt.

International Surfacing Systems and C.H. Mc Donald had developed a way of taking granulated rubber from old tires and turning it into a visco-elastic binder by blending it with asphalt (bitumen). This patented process has been used now for over 30 years with success and has spread to many countries around the world. This includes, Australia, South Africa, Portugal and Korea.

This process combines the aims of road rehabilitation with environmental responsibility.

Under constant technical improvement, the product is suitable for high and low temperature applications for crack relief and the construction of durable hot mix and chip sealed pavement structures.

In 1996 ISI became ISS and a part of the VSS group of companies and Via WSS asphalt rubber is made and used in California under the Reed group pf Companies.

AR has been used extensively in California and Arizona for decades with great success.
What are the Other Processes?
There are two other ways that have been used of adding rubber to binders. The first is the dry process where the rubber essentially becomes a part of the aggregate system. Some modification of the binder is claimed, however this is not as efficient as the wet process.
Terminal blends incorporate the rubber at the refinery or central blend plants. Such materials are relatively new and use synthetic polymers with lower percentages of crumb rubber than AR.

AR using the wet process gives, by far the greatest benefits.
Benefits Of Asphalt Rubber
Asphalt rubber can be used as a stress absorbing membrane seal, a stress absorbing membrane interlayer between a cracked surface and an overlay of hot mix .

Asphalt Rubber significantly improves

  1. Fatigue crack resistance
  2. Low temperature cracking resistance
  3. Rut resistance
  4. Resistance to bleeding
  5. Aging Resistance
  6. Stone retention

This means it is the best type of binder to use in:

  1. Hot mix overlays on PCC on Asphalt Pavements
  2. SAM and SAMI seals
  3. Surface Chip Seals
  4. Cape Seals
ASPHALT RUBBER:
  • Reduces traffic noise
  • Reduces maintenance costs by extending the life of fatigued roads and reducing thickness requirements for overlays by up to half.
  • Conserves natural resources as it uses old tires
  • May be used in initial construction to extend road life
  • Will improve skid resistance and drainage of road surfaces when used as gap or open graded mixes
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