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Performance Grade bitumen

Performance Grade bitumen, The Superpave Binder specification and the supporting test procedures are products of the Strategic Highway Research Program (SHRP), a 5-year research effort (1987 to 1992) which targeted $50 million for asphalt research.

Penetration grading and viscosity grading are somewhat limited in their ability to fully characterize asphalt binder for use in HMA pavement but Superpave performance grading (PG) tests and specifications are specifically designed to address HMA pavement performance parameters such as rutting, fatigue cracking and thermal cracking.

Superpave performance grading (PG) is based on the idea that an HMA asphalt binder’s properties should be related to the conditions under which it is used. For asphalt binders, this involves expected climatic conditions as well as aging considerations. Therefore, the PG system uses a common battery of tests (as the older penetration and viscosity grading systems do) but specifies that a particular asphalt binder must pass these tests at specific temperatures that are dependent upon the specific climatic conditions in the area of use.

PG system is based on project climate. The standard notation for PG binder is PG XX-YY where XX is the average-seven-day maximum pavement design temperature and YY is the minimum pavement design temperature. able 1 shows how the Superpave PG system addresses specific penetration, AC and AR grading system general limitations.

Limitations of Penetration, AC and AR Grading Systems

Penetration and ductility tests are empirical and not directly related to HMA pavement performance.

 

Tests are conducted at one standard temperature without regard to the climate in which the asphalt binder will be used.

 

The range of pavement temperatures at any one site is not adequately covered. For example, there is no test method for asphalt binder stiffness at low temperatures to control thermal cracking.

 

Test methods only consider short-term asphalt binder aging (thin film oven test) although long-term aging is a significant factor in fatigue cracking and low temperature cracking.

 

Asphalt binders can have significantly different characteristics within the same grading category.

 

Modified asphalt binders are not suited for these grading systems.

 

 

Superpave Binder Testing and Specification Features that Address Prior Limitations

The physical properties measured are directly related to field performance by engineering principles.

 

Test criteria remain constant, however, the temperature at which the criteria must be met changes in consideration of the binder grade selected for the prevalent climatic conditions.

 

The entire range of pavement temperatures experienced at a particular site is covered.

 

Three critical binder ages are simulated and tested:
1. Original asphalt binder prior to mixing with aggregate.
2. Aged asphalt binder after HMA production and construction.
3. Long-term aged binder.

 

Grading is more precise and there is less overlap between grades.

 

Tests and specifications are intended for asphalt “binders” to include both modified and unmodified asphalt cements.

 

 

Specification

PG 46-34 PG 46-28 PG 52-28 PG 58-28 PG 58-22 PG 64-22 AASHTO Method
Original Binder
Flash Point, COC,°C 230 T 48
Flash Point, P-M, °C NS ≥ 204 ASTM D93
Rotational Viscosity @ 135°C, Pa·s 3.00 T 316
Dynamic Shear @ Grade Temperature,°C 46 46 52 58 58 64 T 315
G*/sin @ 10 rad/sec, kPa ≥ 1.00
RTFOT Residue
Mass Loss, % ≤ 1.00 T 240
Dynamic Shear @ Grade Temperature,°C 46 46 52 58 58 64 T 315
G*/sin @ 10 rad/sec, kPa 2.20
PAV Residue (Aging Temperature, °C) 90 100 R 28
Dynamic Shear @ Grade Temperature,°C 10 13 16 19 22 25 T 315
G*/sin @ 10 rad/sec, kPa 5000
Creep Stiffness -24 -18 -18 -18 -12 -12
S, Mpa ≤ 300 T 313
m-value ≥ 0.30 T 313

 

Table . Performance Grade Bitumen Specification

Specification

 Performance Grade bitumen Specification