Viscosity of Asphalt Binder/Bitumen: Standards and Method for Enhancing Asphalt Quality

Quality control of asphalt involves various elements, but among them, viscosity measurement of asphalt binder is crucial not only for the ease of asphalt construction but also significantly impacts the quality aspects such as durability. If the viscosity is too high, construction becomes difficult, leading to extended construction periods and increased costs. Conversely, if it's too low, roads are prone to deformation. Properly designing and managing the viscosity of asphalt is extremely important for high-quality asphalt pavement. Viscosity measurement is carried out in various stages, from the design and manufacturing of asphalt binder to the management of the quality of asphalt materials used by paving contractors, encompassing different processes from the production of asphalt ingredients to construction. Additionally, the viscosity of asphalt binder is also a vital indicator for its transportability via pump trucks.

Standards for viscosity measurement of asphalt binder

ASTM D4402 and AASHTO T316 are well-known as representative standards for asphalt viscosity measurement.

ASTM D4402

ASTM D4402 is a test method designed to evaluate the dynamic properties of asphalt binders and confirm the performance of asphalt at elevated temperatures. This is essential for quality control, research and development, and for formulating asphalt mixtures for different environmental conditions. Used in the design of durable road surfaces and construction projects.

Purpose

Evaluation of flow characteristics and applicability by measuring the viscosity of asphalt binder at high temperatures

Equipment Used

Rotational viscometer

Test conditions

• Conducted in a high temperature environment of 135-165℃
• The sample is a homogeneous, contaminant-free asphalt binder.
• Preheat to test temperature in advance

Measurement

Rotate the rotor and measure the resistance to rotation of the binder

Unit

centipoise (cP)

AAHTO T316

AASHTO T316 is a test method aimed at evaluating the dynamic properties of asphalt binders to improve the quality and durability of road pavements. This is essential for asphalt binder selection and characterization. It is used to guarantee the long-term performance of asphalt pavement.

Purpose

Evaluation of dynamic shear properties of asphalt binder

Application

Used in the superpave asphalt mixture design system

Equipment Used

Super Pave Shear Tester (SST)

Test conditions

• Conducted in a high temperature environment of 46℃ to 82℃

• Sample is asphalt binder free of contaminants

Measurement

Applying shear force to an asphalt binder sample and measuring the response using SST

Practice of asphalt binder viscosity measurement with rotational viscometer

The standards mentioned in the previous section introduce viscosity measurements using a rotational viscometer.
For example, ASTM D4402 specifies the following procedures for conducting measurements:

• Calibration
• Heating the sample in a constant temperature bath
• Viscometer setup, including equipment installation, correct rotor selection, and range setting
• Measurement, where multiple readings are taken and the results are averaged.
• Reporting

VT-06 Rotational Viscometer

VT-06, while adopting a rotational method, offers ease of use in the field with its effortless handling. Being portable and cost-effective, it can be easily introduced to various sites with measurement needs. For instance, in the asphalt industry, it finds applications ranging from asphalt construction sites to quality control of asphalt binder.