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Rubber Scrap - The Unique Strategy for Tyre Scrap Management

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by - 12/21/2015 3826 Views

Rubberized Asphalt Concrete (RAC)

What is Rubberized Asphalt Concrete?

Rubberized Asphalt Concrete (commonly known as RAC) is an innovative material for paving roads, which is made by blending ground-up tires scrap with asphalt to produce a binder which is then mixed with conventional aggregate materials. This mix is then placed and compacted into a road surface. There are two primary types of binders for RAC, asphalt-rubber and terminal blend.

Asphalt-Rubber: Asphalt-rubber is defined by American Society for Testing and Materials (ASTM) Standard D6114 as "a blend of paving grade asphalt cement, ground recycled tire (that is, vulcanized) 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." The asphalt-rubber binder is field blended (at the hot mix plant) and requires specialized mobile mixing equipment to produce. Typical crumb rubber modifier (CRM) content for asphalt-rubber ranges from 18-22 percent. The crumb rubber modifier used in asphalt-rubber is in the 10-16 mesh range. Asphalt-rubber been successfully used in California for over 30 years.

Terminal Blend: Terminal blends are the binder materials that use finely ground (less than 30 mesh) crumb rubber scrap modifier and are typically blended at the asphalt refinery. Historically, terminal blend binders contained 10 percent or less crumb rubber modifier. However, in recent years the crumb rubber modifier content has been increased to 15-20 percent in some projects. Terminal blend has 20 years of successful use in California.

Why Use RAC?

RAC is a proven product with many benefits, including being cost effective, durable, safe, quiet, and an environment friendly alternative to traditional road paving materials.

Cost-effective: In most applications, RAC can be used at a reduced thickness compared to conventional asphalt overlays--in some cases at half the thickness of conventional material--which may results in significant material reduction and cost savings. In addition there may be life-cycle cost savings from the reduction in maintenance costs and longevity of RAC.

Durable, Safe and Quiet: RAC is best known for its durability and is long lasting. It resists cracking, which can reduce maintenance costs. Case studies have demonstrated repeatedly that RAC, when designed and constructed properly, lasts much longer--often 50 percent longer--than conventional materials. Additionally, RAC provides better skid resistance, which can provide better traction. Moreover, RAC retains its darker color longer so that road markings are more clearly visible and can reduce road noise.

Environment Friendly: In the United States, California alone is responsible for producing more than 40 million waste tyre rubber scrap annually, of which approximately 75 percent are diverted from landfill disposal. The state still faces the challenge of dealing with roughly10 million surplus tires annually. The majority end up in our landfills but some end up in illegal stockpiles. A two-inch-thick RAC resurfacing project uses about 2,000 scrap tires per lane mile. Over the past few years, California has used more than 10 million waste tire scrap in RAC paving projects, diverting them from landfills or illegal disposal.

There are many other added advantages also for using rubberized asphalt versus conventional asphalt. RAC incorporates ground tyre (crumb) rubber scrap into the hot mix. Crumb rubber is ground or granulated rubber particles, which are derived from auto or light truck tires or other sources that use a high content of natural rubber. The wet process is typically used in rubberized asphalt within the State of California. The wet process mixes the rubber with the binder (80% asphalt cement / 20% crumb rubber) in a field blending unit prior to introduction at the hot mix plant.

The State of California, Department of Transportation is responsible for the design, construction, maintenance, and operation of the California State Highway System or otherwise known as Caltrans began experimenting with rubberized asphalt produced by the "wet process" in the 1970's and developed design criteria using roadway deflection testing that resulted in thinner overlay courses than conventional asphalt concrete. Research has shown that 4" of conventional asphalt can be replaced with 2" of rubberized asphalt to achieve the same fatigue life. In the early 1990s, Caltrans testing confirmed the reduced thickness design of a gap-graded mix and received approval from the Federal Highway Administration. 

The stated advantages of Rubberized Asphalt Concrete are as follows:

  1. Rubber Cape sealing can extend the life of a street by 10-14 years.
  2. Rubberized Asphalt Concrete is highly skid-resistant, quieter and resists shoving and rutting if a gap-graded mix is used.
  3. Rubberized asphalt concrete is environmentally friendly. A two-inch resurfacing project can use approximately 500 waste tires per lane mile.
  4. Rubberized asphalt concrete provides excellent long-lasting color contrast for striping and marking.
  5. Rubberized asphalt concrete provides a long-lasting, durable pavement that resists reflective cracking.

Category : Rubber

Tags : Rubber Tyre Scrap, Rubber Tyre Scrap Market, Rubber Tyre Scrap Price, Rubber Tyre Scrap Benefits, Rubber Tyre Scrap Current Trend

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About Georgy Abraham

As the bright morning of 28th May dawned in the year 1972, in the fulfillment of time according to the plan & will of Almighty Godbrought me forth into this world and I was brought up & educated in Orissa. My parents provided me with the best of education in an English medium school with high standa .... more info


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