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AASHTO T121 – Standard Method of Test for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete


AASHTO T121 is a standard test method used to determine the density (unit weight), yield, and air content of freshly mixed concrete. This test is essential for quality control in concrete production and construction, ensuring that the concrete mix meets the specified requirements for strength, durability, and workability.

Key aspects of AASHTO T121:

  • Density (unit weight): the density of concrete is determined by measuring the mass of a known volume of freshly mixed concrete. This information is used to calculate the unit weight, which is the mass per unit volume of concrete.
  • Yield: the yield of concrete is the volume of concrete produced from a known mass of the constituent materials. This is calculated using the density of the concrete and the mass of the ingredients.
  • Air content: the air content of concrete is the volume of air voids entrapped in the concrete mix, expressed as a percentage of the total volume. The air content is determined by comparing the theoretical mass of the concrete (calculated from the mix proportions) to the actual mass of the concrete sample.


  • A calibrated container of known volume is filled with freshly mixed concrete.
  • The concrete is consolidated to eliminate air pockets and voids.
  • The mass of the filled container is determined.
  • The density and unit weight of the concrete are calculated.
  • The yield and air content are calculated using the density and the known mass of the ingredients.

Significance of AASHTO T121:

  • Quality control: by measuring the density, yield, and air content of concrete, contractors and producers can ensure that the concrete mix meets the specified requirements.
  • Mix design: the test results can be used to optimize the mix design of concrete by adjusting the proportions of the ingredients to achieve the desired properties.
  • Performance prediction: the density, yield, and air content are important parameters that influence the strength, durability, and workability of concrete.

AASHTO T121 Accredited Laboratory

Applied Testing & Geosciences, LLC is accredited for performing tests using the AASHTO T121 standard.

Our laboratory offers comprehensive concrete testing services, including the determination of density, yield, and air content according to AASHTO T 121. Our experienced technicians utilize standardized procedures and calibrated equipment to ensure accurate and reliable results.

Contact us for more information.



density; yield; air content; concrete; unit weight; mass; volume; gravimetric method; tamping rod; calibration; freshly mixed concrete