The article titled "Editorial: Rubberized asphalt finally arrives" in Global Tire News (November 5, 2012) provides a historical review of past experiences with the use of recycle tire rubber (RTR) but falls short in informing readers of current practices and future use of RTR as an asphalt modifier.
Sir:
Your “Editorial: Rubberized asphalt finally arrives” in Global Tire News (November 5, 2012)
provides a historical review of past experiences with the use of recycle tire rubber (RTR) but falls
short in informing your audience of current practices and future use of RTR as an asphalt
modifier.
First and foremost – and contrary to your conclusion – there is no shortage of RTR to meet the
needs of the asphalt paving industry, nor is any type of shortage expected in the future.
Specifications put into place in the late 1990s eliminated the possibility of using RTR as a
modifier in Superpave mix designs and Performance Graded asphalt. The specifications were
designed around two components, liquid asphalt binder and stone aggregate. A third component
such as rubber was not allowed or well understood. Now, DOTs have begun to remove the
specification barriers and allow RTR as an alternative modifier.
As you rightly note, since then the world of petroleum products has turned upside down and
asphalt has increased in cost from about $60 per ton to today as much as $600 a ton. Today, the
most common asphalt modifier, namely polymers, now may cost as much $1,000 per ton and
availability at times is in doubt. In contrast, RTR as a modifier has remained at approximately
$300 per ton, even less expensive than asphalt and is readily available.
Likewise the array of RTR products has increased and continues to grow. RTR asphalt products
now include the traditional asphalt-rubber as defined by ASTM at 15% or more RTR by weight of
asphalt, as well as asphalt light RTR asphalt products containing 5 to 14% RTR by weight of
asphalt, hybrid RTR asphalt products that contain both RTR and polymer and a new type of RTR
asphalt product that includes RTR, asphalt and a special activated mineral.
Additionally, RTR asphalt products can be field blended, terminal blended and delivered in a
pelletized form. Some states specify RTR asphalt as a PG graded asphalt in a manner similar to
polymer asphalt. (For more information about this wide array of RTR products your readers can
visit the Rubberized Asphalt Foundation website www.RA-Foundation.org, or the Rubber
Pavements Association website www.rubberpavements.org.)
Furthermore, less than 2 weeks ago an international Asphalt Rubber Conference (AR2012) was
held in Munich, Germany where over 20 countries documented current research around the
world on RTR asphalt. (For information about acquiring the book of Proceedings, CD of the
Proceedings and/or video of the speakers they can contact Dr. Jorge Sousa,
jmbsousa@aol.com, or George Way, wayouta@cox.net.)
You are very correct that there has been an amazing turnaround and RTR is now well positioned
to become a routine beneficial modifier which complements and enhances the good properties of
asphalt. The benefits continue to be documented and include better pavement performance at
less cost, as well as an environmentally friendly and sustainable green product.
RTR in asphalt is where the rubber meets the rubber.
Thank you,
George Way, P.E.
Chairman,
Rubberized Asphalt Foundation