Asphalt Pavement Magazine - May/June 2018 - 33

E

however, this mandate was later
repealed and interest in using
rubber in asphalt mixtures subsided
in many states. While some states
ignored the use of rubber, other
states such as California, Arizona,
and Florida began developing rubber
programs and specifications for its
inclusion in asphalt mixtures.
In 2008, a polymer shortage
caused the price of polymermodified asphalt binders to rise
and left many agencies wanting
another tool to use in place of
polymer or as an extender to use
with lesser quantities of polymer.
The solution that many agencies
turned to was RTR. In August of
2010, the Alabama Department of
Transportation (ALDOT) placed its
first RTR-modified asphalt mixture
in over a decade outside of Dothan,
Ala., on US-231 South. Blacklidge
Emulsions terminally blended
the RTR-modified binder, which
contained approximately 11 percent
RTR and a crosslinking agent before
it was delivered to APAC Midsouth
in Dothan. This produced a binder
that would pass the PG 76-22
requirement for the DOT.

While laboratory
testing can be used to
evaluate and predict
mixture performance
in the field, the ultimate
proof of a technology's
appropriateness is field
performance.
An experiment developed by
the National Center for Asphalt
Technology (NCAT) and ALDOT
would compare the performance of
the RTR-modified asphalt mixture to
that of a polymer-modified asphalt
mixture in both the laboratory and
the field. Both 19.0 mm maximum
aggregate size mixtures contained
the similar aggregate structures
of granite, limestone, screenings,
shot gravel, sand and 20 percent
RAP. Due to the differences in the
RTR and SBS modified binders, the
asphalt contents of the mixtures and
continued on page 35

© PHOTO COURTESY TOMMY JAMES AND DAVID FARRIS

ach year the United States
generates approximately
290 million scrap tires.
Of these 290 million
tires, approximately
80.4 percent are recycled or
reused in fuel, agricultural or
civil engineering markets, leaving
27 million tires to be placed in
landfills or stockpiles. Currently,
about 12 million scrap tires each
year are being converted into
recycled tire rubber (RTR) for
modifying asphalt binders.
The utilization of scrap tire
rubber in asphalt started in the mid1960s, when ground rubber was
placed in asphalt surface treatments
such as chip seals. Later in the
1970s, RTR-modified asphalt chip
seals were used as a stress absorbing
membrane interlayer. Its use
extended to asphalt mixtures and
has continued to evolve due to the
rubber's enhancement of mixture
performance, including improved
rutting and cracking resistance.
In the early 1990s, the use of
rubber was mandated for agencies,
and contractors were required to use
rubber in their asphalt mixtures;

The rubber-modified mixture had equivalent or better performance than the polymer-modified mixture.
Asphalt Pavement Magazine - May/June 2018 * 33



Table of Contents for the Digital Edition of Asphalt Pavement Magazine - May/June 2018

Chairman’s Commentary
Industry News
Tools for the Trade
A Green Answer for Higher Recycling
Reducing Rolling Resistance to Reduce Emissions
Recycled Tire Rubber Mixture Yields High-Performing Road
The Pavement Economics Committee: A Powerful Partnership
Focus on the Field: Job Spotlight
Industry Events
Index of Advertisers/Advertisers.com
Perspectives
Asphalt Pavement Magazine - May/June 2018 - intro
Asphalt Pavement Magazine - May/June 2018 - cover1
Asphalt Pavement Magazine - May/June 2018 - cover2
Asphalt Pavement Magazine - May/June 2018 - 3
Asphalt Pavement Magazine - May/June 2018 - 4
Asphalt Pavement Magazine - May/June 2018 - 5
Asphalt Pavement Magazine - May/June 2018 - 6
Asphalt Pavement Magazine - May/June 2018 - 7
Asphalt Pavement Magazine - May/June 2018 - 8
Asphalt Pavement Magazine - May/June 2018 - Chairman’s Commentary
Asphalt Pavement Magazine - May/June 2018 - 10
Asphalt Pavement Magazine - May/June 2018 - Industry News
Asphalt Pavement Magazine - May/June 2018 - 12
Asphalt Pavement Magazine - May/June 2018 - 13
Asphalt Pavement Magazine - May/June 2018 - 14
Asphalt Pavement Magazine - May/June 2018 - 15
Asphalt Pavement Magazine - May/June 2018 - 16
Asphalt Pavement Magazine - May/June 2018 - 17
Asphalt Pavement Magazine - May/June 2018 - Tools for the Trade
Asphalt Pavement Magazine - May/June 2018 - 19
Asphalt Pavement Magazine - May/June 2018 - 20
Asphalt Pavement Magazine - May/June 2018 - 21
Asphalt Pavement Magazine - May/June 2018 - A Green Answer for Higher Recycling
Asphalt Pavement Magazine - May/June 2018 - 23
Asphalt Pavement Magazine - May/June 2018 - 24
Asphalt Pavement Magazine - May/June 2018 - 25
Asphalt Pavement Magazine - May/June 2018 - 26
Asphalt Pavement Magazine - May/June 2018 - 27
Asphalt Pavement Magazine - May/June 2018 - Reducing Rolling Resistance to Reduce Emissions
Asphalt Pavement Magazine - May/June 2018 - 29
Asphalt Pavement Magazine - May/June 2018 - 30
Asphalt Pavement Magazine - May/June 2018 - 31
Asphalt Pavement Magazine - May/June 2018 - Recycled Tire Rubber Mixture Yields High-Performing Road
Asphalt Pavement Magazine - May/June 2018 - 33
Asphalt Pavement Magazine - May/June 2018 - 34
Asphalt Pavement Magazine - May/June 2018 - 35
Asphalt Pavement Magazine - May/June 2018 - 36
Asphalt Pavement Magazine - May/June 2018 - 37
Asphalt Pavement Magazine - May/June 2018 - 38
Asphalt Pavement Magazine - May/June 2018 - 39
Asphalt Pavement Magazine - May/June 2018 - The Pavement Economics Committee: A Powerful Partnership
Asphalt Pavement Magazine - May/June 2018 - 41
Asphalt Pavement Magazine - May/June 2018 - 42
Asphalt Pavement Magazine - May/June 2018 - 43
Asphalt Pavement Magazine - May/June 2018 - 44
Asphalt Pavement Magazine - May/June 2018 - 45
Asphalt Pavement Magazine - May/June 2018 - 46
Asphalt Pavement Magazine - May/June 2018 - 47
Asphalt Pavement Magazine - May/June 2018 - Focus on the Field: Job Spotlight
Asphalt Pavement Magazine - May/June 2018 - 49
Asphalt Pavement Magazine - May/June 2018 - 50
Asphalt Pavement Magazine - May/June 2018 - 51
Asphalt Pavement Magazine - May/June 2018 - Industry Events
Asphalt Pavement Magazine - May/June 2018 - 53
Asphalt Pavement Magazine - May/June 2018 - 54
Asphalt Pavement Magazine - May/June 2018 - Index of Advertisers/Advertisers.com
Asphalt Pavement Magazine - May/June 2018 - 56
Asphalt Pavement Magazine - May/June 2018 - 57
Asphalt Pavement Magazine - May/June 2018 - Perspectives
Asphalt Pavement Magazine - May/June 2018 - cover3
Asphalt Pavement Magazine - May/June 2018 - cover4
http://www.nxtbook.com/naylor/NAPS/NAPS0318
http://www.nxtbook.com/naylor/NAPS/NAPG0018
http://www.nxtbook.com/naylor/NAPS/NAPS0218
http://www.nxtbook.com/naylor/NAPS/NAPS0118
http://www.nxtbook.com/naylor/NAPS/NAPS0617
http://www.nxtbook.com/naylor/NAPS/NAPS0517
http://www.nxtbook.com/naylor/NAPS/NAPS0417
http://www.nxtbook.com/naylor/NAPS/NAPS0317
http://www.nxtbook.com/naylor/NAPS/NAPS0217
http://www.nxtbook.com/naylor/NAPS/NAPS0117
http://www.nxtbook.com/naylor/NAPS/NAPS0616
http://www.nxtbook.com/naylor/NAPS/NAPS0516
http://www.nxtbook.com/naylor/NAPS/NAPS0416
http://www.nxtbook.com/naylor/NAPS/NAPS0316
http://www.nxtbook.com/naylor/NAPS/NAPG0016
http://www.nxtbook.com/naylor/NAPS/NAPS0216
http://www.nxtbook.com/naylor/NAPS/NAPS0116
http://www.nxtbook.com/naylor/NAPS/NAPS0615
http://www.nxtbook.com/naylor/NAPS/NAPS0515
http://www.nxtbook.com/naylor/NAPS/NAPS0415
http://www.nxtbook.com/naylor/NAPS/NAPS0315
http://www.nxtbook.com/naylor/NAPS/NAPG0015
http://www.nxtbook.com/naylor/NAPS/NAPS0215
http://www.nxtbook.com/naylor/NAPS/NAPS0115
http://www.nxtbook.com/naylor/NAPS/NAPS0614
http://www.nxtbook.com/naylor/NAPS/NAPS0514
http://www.nxtbook.com/naylor/NAPS/NAPS0414
http://www.nxtbook.com/naylor/NAPS/NAPS0314
http://www.nxtbook.com/naylor/NAPS/NAPS0214
http://www.nxtbook.com/naylor/NAPS/NAPS0114
http://www.nxtbook.com/naylor/NAPS/NAPS0613
http://www.nxtbook.com/naylor/NAPS/NAPS0513
http://www.nxtbook.com/naylor/NAPS/NAPS0413
http://www.nxtbook.com/naylor/NAPS/NAPS0313
http://www.nxtbook.com/naylor/NAPS/NAPG0013
http://www.nxtbook.com/naylor/NAPS/NAPS0213
http://www.nxtbook.com/nxtbooks/naylor/NAPS0113
http://www.nxtbook.com/nxtbooks/naylor/NAPS0612
http://www.nxtbook.com/nxtbooks/naylor/NAPS0512
http://www.nxtbook.com/nxtbooks/naylor/NAPS0412
http://www.nxtbook.com/nxtbooks/naylor/NAPS0312
http://www.nxtbook.com/nxtbooks/naylor/NAPS0212
http://www.nxtbook.com/nxtbooks/naylor/NAPS0112
http://www.nxtbook.com/nxtbooks/naylor/NAPS0611
http://www.nxtbook.com/nxtbooks/naylor/NAPS0511
http://www.nxtbook.com/nxtbooks/naylor/NAPS0411
http://www.nxtbook.com/nxtbooks/naylor/NAPS0311
http://www.nxtbook.com/nxtbooks/naylor/NAPS0211
http://www.nxtbook.com/nxtbooks/naylor/NAPS0111
http://www.nxtbook.com/nxtbooks/naylor/NAPS0610
http://www.nxtbook.com/nxtbooks/naylor/NAPS0510
http://www.nxtbook.com/nxtbooks/naylor/NAPS0410
http://www.nxtbook.com/nxtbooks/naylor/NAPS0310
http://www.nxtbook.com/nxtbooks/naylor/NAPS0210
http://www.nxtbook.com/nxtbooks/naylor/NAPS0110
http://www.nxtbook.com/nxtbooks/naylor/NAPS0609
http://www.nxtbook.com/nxtbooks/naylor/NAPS0509
http://www.nxtbook.com/nxtbooks/naylor/NAPS0409
http://www.nxtbook.com/nxtbooks/naylor/NAPS0309
http://www.nxtbook.com/nxtbooks/naylor/NAPS0209
http://www.nxtbook.com/nxtbooks/naylor/NAPS0109
http://www.nxtbook.com/nxtbooks/naylor/NAPS0608
http://www.nxtbook.com/nxtbooks/naylor/NAPS0508
http://www.nxtbook.com/nxtbooks/naylor/NAPS0408
http://www.nxtbook.com/nxtbooks/naylor/NAPS0308
http://www.nxtbook.com/nxtbooks/naylor/NAPS0208
http://www.nxtbook.com/nxtbooks/naylor/NAPS0108
http://www.nxtbook.com/nxtbooks/naylor/NAPS0607
http://www.nxtbook.com/nxtbooks/naylor/NAPS0907
http://www.nxtbook.com/nxtbooks/naylor/NAPS0407
http://www.nxtbook.com/nxtbooks/naylor/NAPS0507
http://www.nxtbookMEDIA.com