Presentation on asphalt binders by Bob Humer, Asphalt Institute, delivered at the California Asphalt Pavement Association (CalAPA) Spring Asphalt Pavement Conference April 25-26, 2018 in Ontario, CA.

1. CalAPA 2018 Spring Conference
Asphalt Institute’s
1970s Logo
Bob Humer
Asphalt Institute

2. The term “binder” covers both neat (unmodified) and
modified asphalt cements, but doesn’t include
emulsions and cutbacks.
Binders are the “glue” that holds the aggregate
together in HMA. It’s the least expensive glue by far.
Unlike emulsions and cutbacks, binders are typically
required to be heated to over 300°F for use, unless
modified for use as Warm Mix Asphalt (WMA).
Polymers can be added to the binder to enhance their
high temperature performance.
What is Asphalt binder?

3. Asphalt Description and Sources
Asphalt Cement or Asphalt Binder
– Black, cementitious, waterproof material
– Originally mined from a natural lake (still operating today:
Lake Asphalt of Trinidad and Tobago)
– Almost all asphalt today comes from crude oil refining.

4. Understanding Asphalt Chemistry
• Asphalt is made up of very large
complex Hydro-Carbon molecules.
• > 10,000 Atomic weight (and much
larger).
• These Hydro Carbon structures have
other trace elements attached.
• No Asphalt molecule is the same as
the next one.
• These molecules are not static (they
change composition) especially at
elevated temperatures.
• To specify Asphalt by chemical
composition is hardly possible.
• That’s why we specify the physical
properties

5. Refining seperates the different fractions
Typical Crude Make-Ups
Venezuelan Arabian-Heavy Nigerian-Light
58 %
27
20
1426 %
28
30
21
33
16
3 % 6 %
7 %
10 %
1 %Asphalt
Residue
Hv. Gas Oil
Lt. Gas Oil
Gasoline
Kerosene

6. Refinery Operation
FIELD STORAGE
PUMPING
STATION
LIGHT DISTILLATE
HEAVY DISTILLATE
PROCESS
UNIT
ASPHALT
CEMENTS
FOR PROCESSING INTO
EMULSIFIED AND
CUTBACK ASPHALTS
STILL
AIR
AIR
BLOWN
ASPHALT
STORAGE
TOWER
DISTILLATION
REFINERY
RESIDUUM
OR
GAS
PETROLEUM
SAND AND WATER
CONDENSERS
AND
COOLERS
TUBE
HEATER
MEDIUM DISTILLATE
6

7. Asphalt does not go into a vapor phase

8. 8
Asphalt is exposed to 800+ °F in Refining

9. vacuum
CANNON
100
A9
Change in Viscosity can indicate “Ageing”
9

10. Asphalt aging over Time
Viscosity
Time
A B
C
D1
D2
D3
Bulk Storage
and Handling
Mixing, Placing,
and Compaction
Long-term, In-place Aging

11. Asphalt Binder Properties
Consistency
Liquid
Semi-Solid
Temperature
Asphalt is a thermoplastic material
that softens as it is heated and
hardens when cooled.
11
Asphalt is also a viscoelastic
material that has both the
properties of an elastic solid and a
viscous liquid, depending on the
temperature.
and

12. Asphalt Flow Behavior
140 F 1 hour
10 hours
77 F
1 hour
at
at

13. • Penetration (from 1904), at 25 C only
• empirical measure of viscous and elastic effects
• Specification Proliferation
• Viscosity (AC and AR Grading, 1970s), at 60 and 135 C
• viscous effects only
• No Low Temperature Properties Measured
• Long Term Aging not Considered
• Problems with Modified Asphalt Characterization.
• PG grading “to the rescue”.
13
Asphalt Grading Systems
Pre-Superpave Shortcomings

14. 25 60 135-15
hard
soft
pen
vis
vis
A
B
C
Temperature, º C
Historic Specifications (Pen and Vis)
14

15. Superpave Asphalt Binder Specification
Grading System Based on
Climate
PG 64-22
Performance
Grade
Average 7-day
max pavement
design temp
Min pavement
design temp
15

16. PG Binder Specifications
The PG grading system is based on Climate
PG 64 - 22
Performance
Grade
Meets all
requirements up to
this temperature
(°C)
Meets all
requirements down
to this temperature
(°C)

17. PG 64-34 (98% minimum reliability)
PG 58-28 (50 % minimum reliability)
PG Binder Selection (for project location)
Binder grades are at 6-degree
increments
-40 -30 -20 -10 0 10 20 30 40 50 60 70
17

18. Pavement Temperature, °C
- 12 25 64 135
PG Specification tests
DSRDSR
BBR
DTT
Vis
Testing for PG 64-2218

19. 19
AASHTO M320 (PG Specification Chart)

20. Grade “Bumping” (high temperature only)
Example
• Toll road
PG 64-22
• Toll booth
PG 70-22
• Weigh stations
PG 76-22
90 kph (55 MPH)
Slow
Stopping
20

21. Is a PG a Modified Binder?
PG 64 - 34 64 - - 34 = >92
Probably modified
Depends on asphalt source
“Rule of 92”
21

22. PG Binder Grades
0 10 20 30 40 50 60-10-20-30-40 70 80
PG 64-22
PG 70-28
The Rule of 90
PG 64-22 Probably Unmodified
PG 70-28 Probably Modified
This is
the
benefit
of the
modifier
TEMPERATURE ºC

23. Cutback Asphalt
• Paving asphalt liquefied by blending with
petroleum solvents
• Resulting material can be sprayed/mixed
at lower temperatures
• Primary uses:
– penetrating prime coat
– binders for storable cold mix asphalt

24. The purpose of diluting the binder with water is to
lower the viscosity.
If the emulsifying agent causes the particles to have a
negative charge, the emulsion is said to be anionic.
This allows the emulsion to be shot onto the roadway
surface at much lower temperatures than straight
binder.
If the emulsifying agent causes the particles to bear a
positive charge, the emulsion is said to be cationic.
Asphalt Emulsions

25. PMAs on average extend Pavement life by 80%
This study (published in Feb
2005) used national field
data to determine enhanced
service life of pavements
containing polymer
modified binders versus
conventional binders. The
data is from a variety of
climates and traffic volumes
within North America.ER 215
IS 215
Asphalt Institute Publications
(IS 215 and ER 215)

26. Asphalt Materials for Paving (US)

27. 2005 Transition from AR to PG grading in CA
To keep things workable, Caltrans agreed to five “neat” binders and 3
“modified” binders only, so a HMA Plant with two binder tanks could operate
with one standard grade for the area and one special grade.
Visit Caltrans COC website for qualified binder Suppliers and grades:
http://dot.ca.gov/hq/esc/Translab/ormt/fpmcoc.htm

28. Asphalt Institute’s Specifications Database
To find all States’ Binder Specifications and grades:
www.asphaltinstitute.org/engineering/specification-databases/

29. 2016 Asphalt Data (paving Asphalt)
Region (less California):
• 1,097K paving tons
• 13.2% increase from 2015
California:
• 1,521K paving tons
• 13.1% increase from 2015
Total for Pacific Coast States:
• 2,619K paving tons
• 13.1% increase from 2015

30. 2016 Asphalt Data Highlights (U.S.)
• 38 MM Tons production capacity (US)
• 23.4 MM Tons produced (US) (all types)
• 3.0 MM Tons imported into US
• 87% paving, 13% non-paving uses in U.S.

31. USA Tonnage History 1999 - 2016

32. Funding History
18.4 cents/gal raised last in 1993 (24.4 cent/gal on diesel)
Erosion of 40% of purchasing power
Ave fuel economy of passenger car up 12% (2005 – 2014)
55% of Americans support an increase

33. MS-26
For More Binder Information
33
MS-25

34. Asphalt Binders 101
Questions ?
Bob Humer, P.E.
Sr. Regional Engineer
Asphalt Institute
Westlake Village, CA
rhumer@asphaltinstitute.org
www.asphaltinstitute.org
CalAPA 2018 Spring Conference