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AASHTO T19 – Standard Method of Test for Bulk Density (“Unit Weight”) and Voids in Aggregate


AASHTO T19 is a standard test method used to determine the bulk density (unit weight) and voids in aggregate. This test is essential for evaluating the properties of aggregates used in various construction applications, such as concrete, asphalt pavements, and base/subbase layers.

Key aspects of AASHTO T19:

  • Bulk density: bulk density is the mass of aggregate per unit volume, including both the solid particles and the voids between them. It is typically expressed in kilograms per cubic meter (kg/m³) or pounds per cubic foot (lb/ft³).
  • Voids: voids are the spaces between the aggregate particles that are not occupied by solid material. The voids content is usually expressed as a percentage of the total volume.
  • Test procedure: the test involves filling a calibrated container of known volume with aggregate and determining its mass. The bulk density is calculated by dividing the mass of the aggregate by the volume of the container. The voids content is calculated by subtracting the volume of the solid aggregate particles (determined from the specific gravity of the aggregate) from the total volume of the container.
  • Compaction: the test can be conducted on both loose and compacted aggregate. For compacted aggregate, the standard specifies different compaction methods depending on the maximum size of the aggregate.

Significance of AASHTO T19:

  • Mix design: the bulk density and voids content of aggregate are important parameters in mix design calculations for concrete and asphalt mixtures. They influence the amount of binder required to achieve the desired properties of the mixture.
  • Quality control: the test is used by aggregate producers and construction contractors to ensure that the aggregates used in their projects meet the specified requirements and quality standards.
  • Performance evaluation: the bulk density and voids content can be used to assess the potential performance of aggregates in specific applications. For example, aggregates with low voids content are generally preferred for concrete pavements because they provide better resistance to the ingress of water and deicing chemicals.

AASHTO T19 Accredited Laboratory

Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T19 standard.

Our laboratory offers comprehensive aggregate testing services, including the determination of bulk density and voids according to AASHTO T19. Our experienced technicians utilize calibrated equipment and adhere to strict quality control procedures to ensure the accuracy and reliability of our test results.

Contact us for more information.



bulk density; unit weight; voids; aggregate; specific gravity; compaction; rodded unit weight; loose unit weight; voids filled with asphalt; voids in mineral aggregate