AASHTO M 320-2023 - Performance - Graded Asphalt Binder

Standard No.: AASHTO M 320-2023
Release Date: 2023
Published By: American Association of State Highway and Transportation Officials US / AASHTO
Latest: AASHTO M 320-2023

Introduction

Technical Analysis of AASHTO M 320-23 Performance-Graded Asphalt Binder Standard

The M 320-23 standard, "Specification for Performance-Graded Asphalt Binders," published by the American Association of State Highway and Transportation Officials (AASHTO) in 2023, represents a major technological advancement in the asphalt material evaluation system. This standard completely changes the traditional empirical grading method and establishes a complete evaluation system based on the actual performance of the pavement.

Standard Framework and Technological Evolution

Since its first release as a complete standard in 2002, the M 320 standard has undergone multiple technical revisions. The most important technical updates to the 2023 edition include: optimization of the LTPPBind temperature prediction model, improvement of the critical cracking temperature determination method, and clear definition of the application scenarios of Tables 1 and 2.

Technical Dimension	Traditional Grading System	Performance Grading System	Technical Advantages
Grading Basis	Empirical Physical Indicators	Actual Pavement Performance Response	Closer to Usage Conditions
Temperature Adaptability	Single Temperature Point Evaluation	Full Temperature Range Performance Coverage	Adaptability to Complex Climates
Aging Evaluation	Short-Term Aging Simulation	Complete Aging Process Simulation	More Accurate Lifespan Prediction
Modifier Compatibility	Limited Evaluation Methods	Complete Performance Characterization	Supporting Technological Innovation

In-Depth Analysis of the PG Grading System

The Performance Grade system is a core technical feature of the M 320 standard. PG grades are notated using the "PG XX-YY" format, where XX represents the maximum design temperature and YY represents the minimum design temperature. Both are calculated using the LTPPBind program.

The LTPPBind temperature prediction model analyzes historical meteorological data to establish a corresponding relationship between air temperature and pavement temperature. This model considers factors such as solar radiation, wind speed, and pavement structure, providing accurate temperature design parameters for specific regions.

Engineering Application Case: PG Grade Selection in Different Climate Zones

In hot regions like Arizona, a PG 76-16 grade may be necessary to resist high-temperature rutting; while in cold regions like Minnesota, a PG 64-34 grade may be required to ensure low-temperature crack resistance. This selection method, based on actual climate conditions, significantly improves pavement service life.

Technical Difference Analysis between Table 1 and Table 2

M 320 standard provides two technical tables, the core difference between which lies in the evaluation method of low temperature performance:

Comparison Dimensions	Table 1 (Traditional Method)	Table 2 (Critical Cracking Temperature Method)
Low Temperature Evaluation Method	Bending Beam Rheometer (T 313) + Direct Tensile (T 314)	R 49 Critical cracking temperature determination
Test complexity	Relatively simple	Requires more temperature points for testing
Accuracy level	Meets conventional requirements	Higher accuracy, especially suitable for harsh environments
Applicable scenarios	General road engineering	Heavy traffic, extreme climate areas

The R 49 method used in Table 2 can more accurately predict the low-temperature cracking behavior of asphalt binder under actual use conditions through multi-temperature point testing and thermal stress calculation.

Key Test Methods and Technical Requirements

Dynamic Shear Rheology Test (T 315)

A dynamic shear rheometer was used to measure the rheological properties of the asphalt binder at various temperatures and frequencies. A minimum G*/sinδ value of 1.00 kPa for the original asphalt ensures high-temperature rutting resistance, while a minimum G*/sinδ value of 2.20 kPa for the RTFOT residue evaluates performance retention after short-term aging.

Bending Beam Rheology Test (T 313)

A bending beam rheometer was used to measure the creep stiffness and m-value of the asphalt at low temperatures. A maximum stiffness of 300 MPa limits material embrittlement, while a minimum m-value of 0.300 ensures stress relaxation capacity; together, these two factors ensure low-temperature crack resistance.

Pressure Aging Vessel Simulation (R 28)

PAV aging simulates the long-term aging process of asphalt during the pavement's service life. Different PG grades correspond to different aging temperatures: 90°C for PG 46-52, 100°C for PG 58 and above, and 110°C in extremely high-temperature areas (≥76°C).

Detailed Explanation of Material Technical Requirements

The standard sets clear requirements for the basic properties of asphalt binders: homogeneity, absence of water and hazardous substances, no foaming when heated at 175°C, and a solubility of at least 99.0%. These requirements ensure the material's basic quality and processing properties.

For modified asphalt, the standard allows the use of any suitable material that can dissolve, disperse, or react to enhance performance, but explicitly excludes fibers or other discrete particles larger than 250 μm.

Implementation Recommendations and Engineering Applications

PG Grade Selection Strategy

Determining the temperature design parameters for the project site using the LTPPBind program is the basis for PG grade selection. It is recommended to consider the following factors: traffic load level, pavement structure type, design service life, and local climate characteristics.

Test Plan Development

A complete quality assurance plan should include raw material acceptance testing, production process control testing, and final product verification testing. Particular attention should be paid to the correspondence between aging simulation testing and actual service conditions.

Handling Special Cases

For PG grades not covered in Tables 1 and 2, the standard allows for the specification of high, low, and intermediate temperatures in 6°C increments. This flexibility provides technical support for special project requirements.

Technology Development Trends and Outlook

With the introduction of the Multiple Stress Creep Recovery (MSCR) test method in the M 332 standard, asphalt binder performance evaluation is moving towards more refined standards. Possible future development trends include performance-based design methods, the integration of intelligent material technologies, and the inclusion of sustainability evaluation indicators. As the most advanced asphalt binder evaluation system currently available, the M 320-23 standard provides a scientific and reliable basis for material selection in road projects, and will undoubtedly promote technological progress and quality improvement across the industry.

AASHTO M 320-2023 Referenced Document

AASHTO M 226 Standard Specification for Viscosity-Graded Asphalt Cement*， 2026-04-15 Update
AASHTO M 332 SPECIFICATION FOR PERFORMANCE-GRADED ASPHALT BINDER USING MULTIPLE STRESS CREEP RECOVERY (MSCR) TEST
AASHTO R 28 Standard Practice for Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV)
AASHTO R 29 Standard Practice for Grading or Verifying the Performance Grade (PG) of an Asphalt Binder*， 2026-04-15 Update
AASHTO R 49 Standard Practice for Determination of Low- Temperature Performance Grade (PG) of Asphalt Binders*， 2026-04-15 Update
AASHTO R 66 Standard Practice for Sampling Asphalt Materials*， 2026-04-15 Update
AASHTO T 240 Standard Method of Test for Effect of Heat and Air on a Moving Film of Asphalt Binder (Rolling Thin-Film Oven Test) (ASTM Designation: D2872-22)*， 2024-05-18 Update
AASHTO T 313 Standard Method of Test for Determining the Flexural Creep Stiffness of Asphalt Binder Using the Bending Beam Rheometer (BBR)
AASHTO T 314 Standard Method of Test for Determining the Fracture Properties of Asphalt Binder in Direct Tension (DT)*， 2024-05-19 Update
AASHTO T 315 Standard Method of Test for Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer (DSR)*， 2025-05-16 Update
AASHTO T 316 Standard Method of Test for Viscosity Determination of Asphalt Binder Using Rotational Viscometer
AASHTO T 44 Solubility of Bituminous Materials
AASHTO T 48 Standard Method of Test for Flash Point of Asphalt Binder by Cleveland Open Cup
ASTM D5546 Standard Test Method for Solubility of Asphalt Binders in Toluene by Centrifuge
ASTM D8 Standard Terminology Relating to Materials for Roads and Pavements
ASTM D95 Standard Test Method for Water in Petroleum Products and Bituminous Materials by Distillation

AASHTO M 320-2023 history

2023 AASHTO M 320-2023 Performance - Graded Asphalt Binder
2024 AASHTO M 320-2022 Standard Specification for Performance-Graded Asphalt Binder
2021 AASHTO M 320-2021 Standard Specification for Performance-Graded Asphalt Binder
2024 AASHTO M 320-2017 Standard Specification for Performance-Graded Asphalt Binder
2024 AASHTO M 320-2016 Standard Specification for Performance-Graded Asphalt Binder
2010 AASHTO M 320-2010 Standard Specification for Performance-Graded Asphalt Binder
2024 AASHTO M 320-2009 Standard Specification for Performance-Graded Asphalt Binder
2024 AASHTO M 320-2005 Standard Specification for Performance-Graded Asphalt Binder
0000 AASHTO M 320-2003
2002 AASHTO M 320-2002 Standard Specification for Performance-Graded Asphalt Binder HM-22; Part IB
1987 DIN 7427:1987 Square drive sockets and hexagon drive extensions for hexagon insert bits

AASHTO M 320-2023Performance - Graded Asphalt Binder