ASTM D7928
Full Name
ASTM D7928 – Standard Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis
Scope
ASTM D7928 provides a standardized procedure for determining the particle size distribution of fine-grained soils. This method analyzes the rate at which soil particles settle in a fluid, correlating settling time to particle size based on Stokes’ Law.
Key aspects of ASTM D7928 include:
- Applicability: this test method is suitable for soils passing the No. 4 (4.75 mm) sieve, focusing on particles smaller than 75 µm (0.075 mm) in diameter.
- Principle: the method utilizes the principle of sedimentation, where coarser particles settle faster than finer particles in a known fluid medium.
- Procedure: a soil suspension is prepared with a dispersing agent to prevent flocculation. The density of the suspension is measured at specific time intervals using a hydrometer. These readings, combined with temperature corrections, are used to calculate the percentage of particles finer than a specific size at each measurement time.
- Calculations: Stokes’ Law is employed to determine the equivalent particle diameter based on the settling velocity. A grain-size distribution curve is then generated, plotting the percentage of particles finer than a given size against the corresponding particle diameter on a logarithmic scale.
Benefits of using ASTM D7928:
- Provides a reliable and repeatable method for determining the particle size distribution of fine-grained soils.
- Offers valuable information for classifying soils according to their engineering properties.
- Essential for various applications such as pavement design, embankment construction, and soil stabilization assessments.
ASTM D7928 Accredited Laboratory
Applied Testing & Geosciences, LLC is accredited for performing tests using the ASTM D7928 standard.
Contact us today to learn more about our testing capabilities and how we can support your business.
Resources
Keywords
sedimentation; hydrometer; particle size distribution; gradation; fine-grained soils; Stokes’ Law; specific gravity; temperature correction; hydrometer correction; dispersion; sedimentation time; particle size analysis; soil mechanics