Analyzing the Density of Asphalt through Helium Pycnometry

The accurate measurement of asphalt density is vital when it comes to ensuring the performance and quality of pavement construction. The BetterPyc 380 offers a hands-free solution for measuring asphalt density, making it a useful tool for enhanced pavement performance.

Asphalt is a commonly utilized construction material, particularly in the construction of pavements and roads. The density of asphalt is a key physical property that directly influences both the performance and quality of the final product.

It is fundamental to accurately measure the density of asphalt to guarantee proper pavement performance.

The ASTM D70 and ASTM D71 standards both advise the use of the water displacement method, employing a glass pycnometer to determine the density of asphalt materials.

However, this method can be both labor-intensive and time-consuming, with factors including sample properties and room temperature possibly impacting the accuracy of the results.

The semi-solid asphalt may also stick to the sides of the container, which makes it challenging to acquire an accurate measurement and also to subsequently clean the container. This article presents an alternative method for determining asphalt density to overcome these challenges.

Analyzing the Density of Asphalt through Helium Pycnometry

Image Credit: Bettersize Instruments Ltd.

The design of the BetterPyc 380 is based on the gas displacement method. It can accurately determine the density of semi-solid and solid materials with a temperature control system.

The BetterPyc 380 is easy, reliable, and efficient, delivering an accurate measurement of asphalt density for enhanced pavement performance.


Approximately 50 g of dry, solid asphalt was crushed into a powder until it all passed through the No. 8 (2.36 mm) sieve. The fines were eliminated by screening the powder through the No. 30 (600 μm) sieve, and a large sample cup was filled between 2/3 and 3/4 with the asphalt powder that was retained on this sieve.

Subsequently, the semi-solid asphalt was poured into a disposable sample cup for ease of handling. Using disposable cups eliminates the challenge of clearing the asphalt that sticks to the wall of the container.

To measure the asphalt density with the BetterPyc 380, the device was set up with the conditions detailed in Table 1.

Table 1. Measurement conditions. Source: Bettersize Instruments Ltd.

Parameter Setting
Temperature 25 °C
Sample cup Large
Gas type Helium
Equilibrium < 0.0050 psig/minute
Purge cycle 5
Purge pressure 19.5 psig
Analysis cycle 3
Analysis pressure 19.5 psig


These conditions were selected based on the asphalt properties. The sample cups were subsequently loaded into the automatic BetterPyc 380 for analysis, and the measurement temperature was controlled at approximately 25 ℃.

The pycnometer is a hands-free solution that provides reliable results within two minutes per cycle.


The results are displayed in Table 2.

The density of the semi-solid asphalt is 1.4735 ± 0.0008 g/cm3 under 25.03 ℃, while that of the solid asphalt is 1.059 ± 0.0013 g/cm3 under 25.05 ℃.

Table 2. Asphalt density measured by the BetterPyc 380. Source: Bettersize Instruments Ltd.

Asphalt Temperature (°C) Measured Density (g/cm3)
1 2 3 Average Std. Dev.
Solid 25.05 1.0607 1.0588 1.0576 1.0590 0.0013
Semi-solid 25.03 1.4722 1.4739 1.4735 1.4735 0.0008


The small standard deviation values exhibit excellent repeatability of the results. This is because of BetterPyc 380’s temperature control system, which enables the user to set the temperature and reduce any changes in volume caused by changes in temperature.

The accuracy and precision of the results are enhanced by the temperature being controlled during the analysis, resulting in more reliable and consistent data.


The density of asphalt is a significant property that influences its overall quality and physical characteristics. The BetterPyc 380 gas pycnometer is a precise and reliable instrument that can automatically measure the density of asphalt samples under specific temperatures.

This information has been sourced, reviewed and adapted from materials provided by Bettersize Instruments Ltd.

For more information on this source, please visit Bettersize Instruments Ltd.


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