This test was used to standardize the penetration grading system approach for specifying asphalt cements. This specification uses the penetration of the original asphalt cement in the grade names. That is, a 120-150 penetration grade asphalt will have a penetration value for the original asphalt of between 120 and 150 tenths of a millimeter.
These disadvantages led to the development of the viscosity grading system in the 1970's which is detailed in ASTM D3381. This one ASTM standard actually contains three separate specifications designated as: Table 1, Table 2, and Table 3. The first two specifications are based on the original properties of the asphalt while the last table is based on the properties of the asphalt after rolling thin film oven aging. Each of these tables and differences between them will be discussed in the following slides.
This figure provides a general comparison of the various traditional specifications. While there is no direct relationship between the specifications, there is a general relationship between stiffness and viscosity. Higher penetration numbers correspond with lower viscosities.
The PG grading system was developed to address the short comings seen in the traditional asphalt cement specifications. This specification is referred to as a binder rather than an asphalt cement specification. The difference is that a binder can be either a neat (unmodified) or modified asphalt cement. The term “asphalt cement” usually refers to an unmodified asphalt cement.
The binder designation is based on expected extremes of hot and cold pavement temperatures.
A subsidiary of
Performance –Graded (PG) Binders
Paramount Petroleum Corporation
14700 Downey Ave
Paramount, CA 90723
Director of Asphalt Technical Services
How it is made
Then & Now
Why, When & How?
How will it affect you?
Production Of Modified Asphalt
Polymer, rubbers, etc…
Production Of Modified Asphalt
Long Term Storage
Up to 2 weeks
& increase viscosity
PG-M, PG-PM, PG-TR
More than 3 weeks
– no heat
PMA (PG-PM, PG-TR, PG-M):
– No heat
– Polymer has the tendency to over swell &
Formation Of Coked Material
Around heating coil
Excessive heat for an extended period
Loss in heat efficiency
– Inspection on yearly basis
– Empty the tank and physically remove the material
around the coils
Hardened asphalt around the heating coils
Very hard & brittle
Heating Oil Leakage
Minor leakage can drop viscosity from
2000 to 100 poise
Monitor viscosity or heating fluid
– Material is transferred to another tank and
re-blend to bring it back to spec.
Good practice to flush the tank after TR or
PM project with HOT neat asphalt.
– Attention to contamination
– Tank completely empty
Truck must be cleaned before loading
Some truckers use diesel oil to prevent
plugging of the valves (BAD PRACTICE)
Area filled with
Viscosity, 60C (140F)
Superpave PG Grading System
Developed in 1990s during SHRP
– Related to Pavement Performance?
Binder Contributions to
– Rutting, Fatigue and Thermal Cracking
Environmental Factors or Climate
In-Service & Construction Temperatures
Short- and Long-Term Aging
Superpave Asphalt Binder
The grading system is based on Climate:
In-Service Pavement Temperatures
PG XX - YY
Average 7-day max
AASHTO and ASTM requirements
And much more!!!
PG for rubberized binders
2007: min. 6.0 lb/ mix ton
2010: min. 7.5 lb / mix ton
2013: min. 10.5 lb / mix ton
$2 for every 12 lb of crumb rubber = 1 PTE
min. 15% crumb tire derived & processed in CA
PG-PM and PG-TR has been combined
under one spec: PG-M
PG58-34M, PG64-28M and PG76-22M
PG76-22R – R18 for Chip Seal
A change order needed for ongoing projects
– New projects will have PG-M
Suppliers will include temp/vis curves for
compaction and construction temp.
Call your supplier for recommendations