Density and Porosity Measurements of Solid Materials

We determine the bulk density and porosity of monolithic materials using the Archimedes method, specifically Method 1 of DIN EN 623-2 and Method A of ASTM D792. This method is suitable for apparent porosity measurements greater than 1% and is essentially the same as ISO 1183.

Method Overview

  1. Dry the Test Sample: The sample is dried in an oven.
  2. Degas the Test Sample: The sample is degassed under reduced pressure.
  3. Immerse in Water: The sample is immersed in water, and the mass of the soaked test piece is determined.

Note: This method is not suitable for materials with an average pore size greater than 200 µm. For polymers with a specific gravity less than 1, we use isopropyl alcohol instead of water.

Sample Preparation

  • Three test samples are typically prepared using a 20 mm diamond abrasive coring bit.
  • Approximately 1 gm of the sample is used for the analysis.
what is density measured in
Figure 1. The Mettler Toledo XS 105 balance with density apparatus used for density and porosity measurements

Apparatus

  • Drying Oven: Maintains a temperature of 110 °C ± 5 °C for drying samples.
  • Balance: An analytical balance with a density measurement apparatus to determine the mass of the immersed and soaked test samples.
  • Vacuum Pump: Reduces pressure to 0.040 Pa (0.0040 mbar) for degassing.
  • Immersion Liquid: Distilled water with a few drops of wetting agent to prevent air bubbles.
how to measure density of a solid
Figure 2. The schematic of the apparatus used to remove air from the sample pores and to soak distilled water into the sample pores.

Procedure

  1. Determine the Mass of Dry Samples:
    • Dry samples in an oven at 110°C overnight.
    • Cool samples in a desiccator to room temperature, then weigh immediately (m1).
  2. Soak the Test Samples:
    • Place the sample in a glass vessel and evacuate to less than 2500 Pa for 15-20 minutes.
    • Introduce distilled water, submerging the sample, and maintain reduced pressure for 30-40 minutes.
    • Allow the vessel to return to ambient pressure for an additional 30-40 minutes.
  3. Determine the Mass of Immersed Samples:
    • Weigh the sample while it is suspended and fully immersed in water (m2).
  4. Determine the Mass of Soaked Samples in Air:
    • Quickly wipe the sample to remove surface droplets without drawing liquid from the pores.
    • Weigh the sample immediately (m3).
how to measure density
Figure 3. The sample is weighed when immersed in distilled water and well soaked.
how do you measure density
Figure 4. The sample is weighed in air after being well soaked in water but dried quickly on the outside surfaces.

Calculating Density and Porosity

Using the three weight measurements, we can calculate:

  • Solid Material Density
  • Bulk Apparent Sample Density
  • Percentage of Porosity Volume

This method, ASTM D792-20, provides a comprehensive understanding of the solid material’s lattice density, average density, and porosity percentage.

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