AASHTO TP 132-2023
Determining the Dynamic Modulus for Asphalt Mixtures Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT)

Standard No.

AASHTO TP 132-2023

Release Date

2023

Published By

American Association of State Highway and Transportation Officials  US  /  AASHTO

Status

Be replaced

Replace By

AASHTO TP 132-2025

Latest

AASHTO TP 132-2025

Introduction

Standard Overview and Technical Background

AASHTO TP 132-23, a key specification technically revised in 2023 by the American Association of State Highway and Transportation Officials, specifically addresses the use of the Asphalt Mixture Performance Tester (AMPT) for determining the dynamic modulus of small-scale specimens. This standard represents the latest development in asphalt mixture performance testing technology and is particularly applicable to densely graded mixtures with a maximum nominal aggregate size of 19.0 mm.

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Core Test Principles and Methods

Dynamic modulus (|E*|), defined as the absolute ratio of the peak-to-peak stress to the peak-to-peak strain of a material under sinusoidal loading, is a key metric for evaluating the viscoelastic properties of asphalt mixtures. During the test, specimens at a specific temperature are subjected to controlled sinusoidal compressive stresses of varying frequencies. The dynamic modulus and phase angle are calculated by measuring the temporal evolution of the applied stress and the resulting axial strain.

Test parameters	Technical requirements	Permissible deviation
Specimen size	Diameter 38mm × Height 110mm	±0.5mm
Test temperature range	4°C to 70°C	±0.5°C
Loading frequency	10Hz, 1Hz, 0.1Hz	±1%
Strain range	50 to 75 microstrain	±5 microstrain

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Equipment system technical requirements

Calibration items	Calibration frequency	Accuracy requirements	Reference standards
Load measurement system	Annual/After moving	±1% of indicated value	ASTM E4/E74
Actuator displacement measurement	Annual/After moving	±0.03mm	ASTM D6027
Specimen deformation measurement	Annual/After moving	±0.0025mm	ASTM D6027
Confining Pressure Measurement System	Annual/After Moving	±1% of Indication Value	ASTM D5720
Temperature Measurement System	Annual/After Moving	±0.25°C	NIST Traceable

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Key Technical Points of the Test Process

The test procedure is strictly executed in the order of temperature from low to high and frequency from high to low to ensure the consistency of the specimen status. Key steps include:

1. Specimen Equilibration Time Control: Determine the equilibration time based on the test setup time and test temperature, as detailed in Table 1.
2. Test Condition Selection: Select the test temperature and loading frequency combination based on the asphalt performance grade.
3. Data Quality Control: Strictly adhere to the data quality statistical requirements in Table 3, including indicators such as deformation drift and peak-to-peak strain range.

Practical Application Case Study

In an interstate highway project, the TP 132-23 standard was used to test the dynamic modulus of a PG 64-22 asphalt mixture. The test results showed a dynamic modulus of 8,500 MPa at a frequency of 10 Hz at 20°C, with a phase angle of 25°. All data quality statistics met the standard requirements, providing reliable mechanical parameter input for pavement structure design.

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Data Quality Assurance System

The standard has established a complete data quality assessment mechanism to ensure the reliability of test results through six key indicators:

Quality indicators	Limit requirements	Abnormal cause analysis	Improvement measures
Deformation drift	Applied load direction or reverse ≤100%	Measuring point separation	Add 5 minutes of static period
Peak-to-peak strain	50-75 microstrain	Improper load level	Adjust load level
Load standard error	≤10%	Applied load is non-sinusoidal	Adjust equipment tuning
Standard deviation of deformation	≤10%	Loose measuring point/signal noise	Check measuring point installation
Deformation uniformity	≤30%	Eccentric loading/non-parallel specimen	Ensure specimen alignment
Phase uniformity	≤3°	Improper measuring point placement	Check measuring point location

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Standard technology evolution and innovation

TP The main technical improvements of the 132-23 standard compared with the earlier version include:

• Standardization of small specimen technology: The first systematic standardization of the test method for 38mm diameter specimens
• Optimization of friction and drag reduction devices: Clarification of the use conditions and limitations of PTFE sheets and latex membranes
• Refinition of temperature balance procedures: A method for determining the balance time based on the test setup time
• Improvement of the data quality indicator system: Quantitative evaluation standards for six quality indicators

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Implementation recommendations and precautions

Based on standard requirements and engineering practice experience, the following implementation recommendations are put forward:

1. Equipment selection and verification: Select an AMPT system that complies with SPT equipment specification Version 3.0, and perform verification ring verification regularly
2. Quality control of specimen preparation: Strictly follow the PP 99 standard test specimens, with a target void ratio of ±0.5%. Test environment stability: Ensure the laboratory temperature is within the range of 17-25°C to avoid external environmental influences. Continuous data quality monitoring: Establish a data quality profile and conduct root cause analysis of abnormal data. Personnel training and certification: Operators should receive professional training, and laboratories should be R18 quality system certified. The implementation of this standard will significantly improve the standardization level of asphalt mixture dynamic performance testing, provide technical support for performance-based pavement design and material evaluation, and promote the development of road engineering in a more refined and scientific direction.