Presentation on Rubber Pavements presented at the CalAPA Fall Asphalt Pavement Conference Oct. 24, 2013 in Sacramento, Calif.

1. CalAPA Conference
Sacramento, CA
October 24, 2013
Asphalt Rubber
Revolution
By
Cliff Ashcroft
President
Rubber Pavements Association

2. If you think you know everything
about asphalt rubber pavements?
Think again!
Major changes in California
regarding AR pavements.

3. Asphalt Rubber History
Asphalt Rubber
Chip Seal (SAM)
A R Chip Seal
Interlayer (SAMI)
AZ
Open-Graded
Hot Mix
CA
Dense-Graded
Hot Mix
Gap-Graded
Hot Mix
1960
1970
1980
1990
2000
2010

4. Definition of Asphalt Rubber
 Uses a minimum of 20 +/- 2 % crumb rubber
 Uses 10 mesh (2mm) crumb rubber
 Reacts/interacts crumb rubber for a minimum of 45
min. at elevated temperatures
 Modifies original properties of asphalt cement
 Only crumb rubber binder with an ASTM definition
and extensive research background

5. What is Asphalt Rubber Binder?
 It is a NON PRORIATARY recipe specification
 A blend of recycled tire rubber, asphalt and extender
oil
 Reacted at high temperatures to significantly modify
the asphalt
 Result is a unique product – asphalt rubber binder
 AR has a 45 year proven performance history

6. How is Asphalt Rubber produced?
Specialized equipment and binder blended
on-site
High shear blender for mixing crumb rubber
with asphalt and modifier
Reaction tank with adequate agitation to
assure proper reaction
All materials are metered-in

7. Asphalt Rubber Blending Schematic
Asphalt Storage
Tank
Heat Tank
Binder
Pumped
to Plant
Crumb
Rubber
High Shear
Blender
Reaction Vessel

8. Heater Blender
Rubber Weigh
Hopper

9. Reaction Vessel
Reaction Vessel
Augers and
Direct Fire Heating

10. Computer Controlled
Accurately Measures
Materials During
Production

12. Components of the Asphalt
Rubber Binder
Crumb rubber modifier (CRM)
Asphalt cement
Asphalt modifier

13. Paving Asphalt
PG 64-16 and PG 58-22 asphalt
(80 +/- 2 %)
Conform to Section 92 “Asphalts”
of the Standard Specifications

14. Asphalt Rubber Binder
Properties
Cone penetration
Resilience
Field softening point
Viscosity

15. Factors Affecting Binder
Properties
Asphalt cement
Amount of crumb rubber
Gradation of crumb rubber
Reaction time and temperature

17. High Viscosity
20 % CRM

18. Asphalt
Rubber
Conv. & Other
Mod. Asphalts

19. 22,937,600 rubber particles
per ton of mix help fight cracking

20. Key to asphalt
rubber is high
viscosity and
reduced aging
properties.
13 Year Old Asphalt Rubber Chip Seal

21. Where have Asphalt Rubber strategies
been used successfully?
AR
Hot Mix
AR
Chip Seals
22 yrs. old
15 yrs. old
AR
AR
Cape Seals
Multi-layer
Strategies
20 yrs. old 10 yrs. old

22. Asphalt Rubber Specifications
Rubberized hot mix asphalt
Type “G”
Type “O”
Type “O-HB”
Asphalt rubber chip seal
Asphalt rubber cape seal
Multi-layer systems

23. What are the major changes
in California (Caltrans)
regarding specifications for
AR pavements?

24. Changes in AR Pavements in
California
Changes in Caltrans specifications
 New Superpave specifications
 Some changes made to Section 39
Changes in testing requirements
 Gyratory compactor
 Hamburg wheel tracking
 Moisture sensitivity, minimum dry and wet strengths
Changes in acceptance requirements
Changes in measuring
 MPQP

25. Changes in Specifications
New Superpave specification developed by
Caltrans with major changes to RHMA
requirements (will be finalized in July 2014)
Some changes also made to Section 39 in
standard specifications
New specs have new requirements for RHMA
Laboratory mix design
Field mix acceptance

26. Changes in Mix Design Testing
Increase in minimum binder content to
7.5 % by total weight of mix (move from
min. 7.0% to 8.1% by dry weight of
aggregate)
However, no change in the minimum void
requirements or aggregate grading
requirements - makes this especially
difficult

27. Changes in Mix Design Testing
 AASHTO T-312 gyratory compactor now required for
compaction during mix design (National Standard from
SHRP)
 Move away from Hveem kneading compactor
 New compaction method in California for all mixes,
labs have very little experience
 Contractor’s/labs need to familiarize themselves with
new method
 New method allows variable compaction to achieve
mix voids requirements (N design 50-150 gyrations and
can increase pressure to 825 kPa)

28. Gyratory
Compactor

29. Changes in Mix Design Testing
AASHTO T-324 (modified) Hamburg testing
requirement
Maximum rut depth requirement of 0.5 inch on
field produced mixes
 Rut depth - minimum number of passes (15,000 to
25,000) depending on type and grade of asphalt
(PG 58, 64 or 70)
 Inflection point - minimum number of passes
(10,000 to 15,000) depending on type on grade
of asphalt (PG 58, 64 or 70)

30. Hamburg Wheel
Tracking Device

31. Changes in Mix Design Testing
AASHTO T-283 (modified) Moisture
Induced Damage Test requirement
Minimum dry strength of 110 psi on
field produced material
Minimum wet strength of 84 psi on field
produced material
Freeze thaw cycle required

32. Changes in Acceptance
Binder content tolerance changed from +/- 0.5%
to - 0.4% +0.5%
In-place mix density requirements changed from
91-97% relative density to 92-97%
Air voids requirement in field changed from +/2% to +/- 1.5%

33. Changes in Measuring
New requirements for AR in the Materials
Plant Quality Program (MPQP)
New requirements for weights and measures
for AR blending and production
New recording requirements
New reporting requirements
Asphalt rubber MPQP requirements are
different from other types of binder
production

34. Use of Warm Mix Technology in
RHMA
Contractor now has the option to use
warm mix technology (WMA) in asphalt
rubber hot mix.
WMA will help offset low temperature
placement problems
WMA will aid in the compaction process

35. WMA Benefits to Contractor
Reduced worker exposure to fumes
Decreased emissions at HMA plant
Savings in energy
Easier permitting
Extended haul distances
Lower odor/fumes
Improved thin lift capabilities
Expanded season

36. What to Expect in the Future
 Performance Grade (PG) AR specification
 Sub-Task Group formed under CT/Industry Rock
Products Committee to work on development of a PG
specification for asphalt rubber - 3 year work plan
 Draft specification developed by Industry
 Initial round robin testing conducted through the
PCCAS to determine feasibility of using Dynamic
Shear Rheometer (DSR) for testing AR binders
 Very successful –results indicate DSR can be used for
testing AR binders
 Second round robin planned for early next year

37. AB 513 (FRAZIER)
Establishes the rubberized asphalt concrete (RAC)
market development act.
Requires CalRecycle to award grants to California
Cities, Counties, and regional park districts.
Requires grants provide $2 for every 12 lbs. of crumb
rubber used in a paving project.
Limited to road rehabilitation, not chip seal projects
which use less crumb rubber.

38. AB 513 (FRAZIER)
Background on why this bill is needed.
CalRecycle collects $40 million annually for its tire fund
from the fee on sale of new tires.
Of all the programs to divert tires from landfills, RAC
grants have had the most success. Environmental groups
support RAC because it is considered the highest and best
use of tire recycling.
Most California Cities and Counties are strapped for
money and even though life cycle costs for RAC are less
than conventional asphalt, local governments look for up
front savings.

39. AB 513 (FRAZIER)
 Conventional asphalt is cheaper up front. Unless they can
get grants, they usually repave with conventional asphalt)
 The RAC grants are so popular in California that this past
year $3 million was allocated for them but there were
almost $10 million in qualified grant applications from
cities and counties.
 Governor Jerry Brown signed AB 513 on October 3,
2013.
 Net result to industry is $7,000,000 +

40. How do you get your bang
for your buck using Asphalt
Rubber design?

41. Reflection Crack Retardation
Equivalencies (ft.)
HMA
RHMA-G
RHMA-G
Over SAMI-R
0.15
0.10
--
0.20
0.10
--
0.25
0.15
--
0.30
0.15
--
0.35
0.15 or 0.20a
0.10 or 0.15a
0.45
0.15/0.15 HMA
0.20
a. Depending on crack width and base conditions

43. 3-Layer AR Cape Seal San Leandro
Original
AR Chip Seal
Microsurfacing as Leveling
Slurry/Micro Surfacing

44. Randolph Avenue
Costa Mesa, CA

45. Costa Mesa 20
years old
37mm ARHM-GG
ARCS
25mm AC

46. Whittier 20
years old
37mm ARHMGG
ARCS
25mm AC

47. Advantages of Asphalt Rubber
Pavement Strategies
50% reduced thickness application
Initial savings
Increased fatigue resistance
Reduced oxidation
Reduced construction time
Increased safety
Savings in energy and natural resources
Lower maintenance cost

48. Thank You
Questions?