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 The major role of the Technical
Advisory Board (TAB) for the Rubber Pavements Association is
to recommend and monitor critical research concerning the use
of Asphalt-Rubber paving materials. The TAB has developed a long
range research and development program for the industry which
was published in 2000 in a booklet entitled "Asphalt-Rubber
Research and Development-An Industry Commitment to Excellence."
Last November the TAB developed
several new projects to be added to the 13 included in the 2000
edition. At the meeting, Californians Richard
Stubstad of ERES Consultants and Jack
Van Kirk, of Basic Resources were charged with updating the book
originally drafted by Larry Smith, of QIS, Florida and Maghsoud
Tahmoressi of PaveTex Engineering and Testing of Texas to include
the new projects and status reports on the originals. The book
will be published soon and will be used by the new foundation
as a basis for many of its grant proposals.
Some of the work is currently being done
by various agencies and companies and the following recap represents
the scope of the work as well as status and estimated completion
dates.
- Research work continues at Arizona State University (ASU)
to characterize asphalt rubber gap graded and open graded
mixes using the four point bending beam test for fatigue life.
Also, the Indirect Tensile test for cold temperature shrinkage
cracks and a variety of triaxial type tests for rutting. This
testing is being done for the Arizona Department of Transportation
and a grant from the Ford Motor Company.Virtually all the
results of this work will be used as input data for the new 2002
AASHTO
Pavement Design Guide. Part of the work, the ASU Buffalo
Range project is
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complete and a final report is available. The ASU/Ford/ADOT
study is underway and should be completed in late 2003.
- The Arizona Department of Transportation (ADOT) has
begun a research project with Mactec Engineering to develop an
asphalt rubber gap graded hot mix design test method. Mactec
will use both the Marshall and the Superpave Gyratory compaction
methods in development of the mix design method. This work will
very likely lead to a new end product type specification for
asphalt rubber gap graded hot mix. The mix design project is
underway and is planned to be completed by the end of 2003.
- The RPA has entered into a research contract for Consulpav
to review the literature on pavement noise and develop a state-of-the-art
Synthesis on this subject. This project will lay the ground work
for future research into why asphalt-rubber gap graded and open
graded mixes reduce tire noise. The Noise Synthesis project is
scheduled for completion in October 2003.
- Clemson University through its Asphalt Rubber Research
Center, ARTS,
will be investigating the effect of the size of rubber particles
on the rheological properties of asphalt rubber binder. No time
line was provided on this project.
- ASTM committee work continues to develop a Standard
Practice guide and Mix Design procedure for open graded friction
courses which includes mixes with asphalt rubber. The ASTM Practice
Guide and Mix Design Standards are moving along at a steady pace
and an optimistic date of publishing would be late 2004.
- The AASHTO Subcommittee on Materials Task Force on
Asphalt-Rubber met in Las Vegas in March to further the development
of recommended Practices for the use Asphalt-Rubber in hot mix
asphalt.
- In June of 2002, the Federal Highway Administration in
cooperation with ADOT and the RPA constructed an asphalt rubber
test section at the Turner Fairbanks research center. This test
section along with other modified asphalt test sections will
be evaluated by the FHWA for rutting and cracking performance
using the ALF loading device. Results of this work may well lead
to a Modified asphalt version of the PG grading chart. An optimistic
date of late 2004 is given for this pooled fund study.
- The Pacific Coast Conference on Asphalt Specifications
is testing asphalt rubber using the Dynamic Shear Rheometer
for the purpose of developing a Superpave Performance Grade (PG)
type of specification. Testing of the Asphalt-Rubber may be completed
in the spring of 2004.
- Caltrans/UC Berkeley and the Rubber AC Task Group
have started a testing project in which 6 sections and five
products will be tested by the HVS and in the laboratory. The
materials include a DGAC at full thickness, an Asphalt-Rubber
GG at half thickness, a Modified Binder (MB) 4 at half thickness
and full thickness, a Modified Binder 15 at half thickness and
a MAC 15 at half thickness. The MB products are terminal blends
and were supplied by Valero and Paramount Petroleum. The purpose
of the study is evaluate the proposed Caltrans MB specification.
No completion date was provided for this research.
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Asphalt-Rubber
Research Activities