RoadScience by Tom Kuennen, Contributing Editor 6 September 2014 Better Roads A fter years of promotion, pavements using asphalt rubber, or rubberized asphalt (there’s a difference), are spreading far and wide in the United States. Formerly a Southwest and California phenomenon – its use is mandated by California law – and a handful of states elsewhere, asphalt pavements containing rubber currently are being used in a majority of states. And while all those states may not have actual specifications for pavements containing rubber, they at least are giving them a try. Use of rubber in asphalt pavements likely will get a boost as the Federal Highway Administration (FHWA) updates its 1992 State of the Practice: Design and Construction of Asphalt Paving Materials with Crumb Rubber Modifier (Search for FHWA-SA-92-022 in Google). In May 2013, representatives from the Rubber Manufactur- ers Association, Tire Industry Association, Rubber Pavements Association, Rubberized Asphalt Foundation, National Asphalt Pavement Association and Liberty Tire Recycling met with FHWA’s John Baxter, associate administrator for infrastructure. Their purpose was to encourage FHWA to update that doc- ument to reflect innovations and changes that have occurred in the rubberized asphalt industry since it was published 22 years ago. A new guide will be produced that will capture the best practices in design, construction, application, testing, storage and handling of rubberized asphalt materials in use today. The guide will help agencies and contractors that are explor- ing the implementation of rubberized asphalt technologies of various kinds by providing specifications and quality control procedures that have been successfully used around the globe. Asphalt containing rubber continues to stretch its way into more state Departments of Transportation. Rubber Expands Photo courtesy of Tom Kuennen Thin overlay of warm mix asphalt contain- ing terminal blend asphalt rubber and Evotherm warm mix additive is placed on Calif. 1, the Pacific Coast Highway, near Fort Bragg two hours after load out
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RoadScienceby Tom Kuennen, Contributing Editor
6 September 2014 Better Roads
After years of promotion, pavements using asphalt
rubber, or rubberized asphalt (there’s a difference),
are spreading far and wide in the United States.
Formerly a Southwest and California phenomenon – its
use is mandated by California law – and a handful of states
elsewhere, asphalt pavements containing rubber currently are
being used in a majority of states. And while all those states
may not have actual specifications for pavements containing
rubber, they at least are giving them a try.
Use of rubber in asphalt pavements likely will get a boost
as the Federal Highway Administration (FHWA) updates
its 1992 State of the Practice: Design and Construction of Asphalt Paving
Materials with Crumb Rubber Modifier (Search for FHWA-SA-92-022 in
Google).
In May 2013, representatives from the Rubber Manufactur-
ers Association, Tire Industry Association, Rubber Pavements
Association, Rubberized Asphalt Foundation, National Asphalt
Pavement Association and Liberty Tire Recycling met with
FHWA’s John Baxter, associate administrator for infrastructure.
Their purpose was to encourage FHWA to update that doc-
ument to reflect innovations and changes that have occurred
in the rubberized asphalt industry since it was published 22
years ago.
A new guide will be produced that will capture the best
practices in design, construction, application, testing, storage
and handling of rubberized asphalt materials in use today.
The guide will help agencies and contractors that are explor-
ing the implementation of rubberized asphalt technologies of
various kinds by providing specifications and quality control
procedures that have been successfully used around the globe.
Asphalt containing rubber continues to stretch its way into more state Departments of Transportation.
Rubber Expands
Phot
o co
urte
sy o
f Tom
Kue
nnen
Thin overlay of warm mix asphalt contain-ing terminal blend asphalt rubber and Evotherm warm mix additive is placed on Calif. 1, the Pacific Coast Highway, near Fort Bragg two hours after load out
Better Roads September 2014 7
Char
ts c
ourt
esy
of P
aola
Ban
dini
, New
Mex
ico
Stat
e Un
iver
sity
Among these innovations are use of recycled tire rubber as
a modifier in PG asphalt binders, sustainable polymer modi-
fication, quiet pavement designs, warm-mix technologies in
combination with rubberized asphalt, binder stabilizers (fiber
replacement) to prevent drain down in permeable, porous and
open graded mixes, use of recycled tire rubber with reclaimed
asphalt pavement and shingles, and reduced thickness designs
for highly modified asphalt rubber mixes.
Rubberized Asphalt Foundation chairman George Way, P.E.,
and Rubber Pavements Association executive director Mark
Belshe, P.E., are providing input to FHWA towards the new
document.
What is asphalt rubber?Asphalt pavements utilizing rubber have a number of permu-
tations.
Asphalt rubber (AR) binder consists of a blend of asphalt
cement, ground recycled tire rubber (crumb rubber), and oth-
er additives such as extender oil, natural rubber and polymers,
as needed, says Paola Bandini, Ph.D., P.E., New Mexico State
University, in his 2011 paper, Rubberized Asphalt Concrete Pavements in
New Mexico. “The rubber content should be at least 15 percent
(by weight) of the total blend to provide acceptable properties
of the material, according to the Standard Specification for Asphalt-