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ASTM D422: Particle-Size Analysis of Soils
The combined sieve and hydrometer gradation of a soil — the legacy method many older project specifications still cite, now succeeded by ASTM D6913 and D7928.
| Designation | ASTM D422 |
| Setting | Laboratory |
| Service line | Construction Materials Testing |
Testing is performed to the current edition of ASTM D422 referenced by your project specification. This page is a plain-language overview, not a substitute for the published standard.
What the ASTM D422 test measures
ASTM D422 is the classic particle-size analysis of soils: a sieve analysis for the sand and gravel fraction and a hydrometer analysis for the silt and clay fraction, combined into one gradation curve from cobbles down to a few microns. It is the test behind the percent gravel, sand, silt, and clay in a geotechnical report.
ASTM withdrew D422 in 2016 and replaced it with ASTM D6913 for the sieve portion and ASTM D7928 for the hydrometer portion. It remains in daily use because thousands of project specifications, state DOT procedures, and older geotechnical reports still cite it, and laboratories hold it on their accreditation scopes for that reason.
How the ASTM D422 test works, step by step
The sample is prepared per ASTM D421 and separated on the No. 10 sieve. The coarse fraction is washed and dry sieved. A portion of the fine fraction is dispersed in water with sodium hexametaphosphate, agitated, and placed in a sedimentation cylinder. A hydrometer is read at set time intervals as particles settle, and Stokes' law converts each reading into the percentage finer than a given particle diameter. The fine fraction is then wash sieved to close the curve where the two procedures meet.
What the numbers mean
The gradation curve gives percent passing every size, from which the coefficient of uniformity and curvature, the fines content, and the clay-size fraction are read. Those numbers drive the USCS classification under ASTM D2487, the select fill decision, drainage and filter design, and, together with the plasticity index, the assessment of expansive potential.
What can throw the result off
Incomplete dispersion of clay clumps, temperature drift in the sedimentation cylinder, reading the hydrometer at the wrong meniscus, and an organic or gypsum-bearing soil that flocculates are the classic problems. Newer D7928 tightens several of these controls, which is a practical reason to specify it.
How we help with ASTM D422 testing
Our laboratory runs the full sieve and hydrometer analysis for specifications that cite D422 and the current D6913 and D7928 methods for those that have moved on, and reports both in the format the engineer's classification needs.
FAQ
Common questions about ASTM D422
My specification calls for D422 but it is withdrawn. What do I get?
We run the procedure as written and report it against the specification you have, and can run D6913 and D7928 instead or in addition if the engineer of record prefers the current methods.
Do I need the hydrometer part?
Only if the fine fraction matters, for clay content, dispersive soil screening, or filter design. Many fill specifications need only the sieve gradation and fines content by ASTM D1140.
What does ASTM D422 cover?
ASTM D422, Particle-Size Analysis of Soils. The combined sieve and hydrometer gradation of a soil — the legacy method many older project specifications still cite, now succeeded by ASTM D6913 and D7928.
Is ASTM D422 a field test or a laboratory test?
Laboratory. ASTM D422 is performed in the Sugar Land, Texas laboratory on samples or specimens delivered under chain of custody, or in a mobile laboratory mobilized to large projects.
Which certification qualifies a technician to run ASTM D422?
NICET Construction Materials Testing (Soils) work elements cover ASTM D422. Technicians running it are trained and checked on this method under the laboratory quality system, with the training record on file.
Which tests are usually run with ASTM D422?
ASTM D421 (Dry Soil Sample Preparation), ASTM D558 (Soil-Cement Moisture-Density), ASTM D698 (Standard Proctor), ASTM D854 (Soil Specific Gravity). A project specification usually calls for them together, and one technician visit or one laboratory sample covers the set.
How do I schedule ASTM D422 testing?
Call (346) 420-5425 for dispatch, or send the specification sections and quantities through the proposal request form for a written scope. Same-day or next-morning scheduling is typical in the Houston metro; other metros are scheduled through the nearest regional hub.
Scheduling & proposals
Need ASTM D422 testing?
Call to schedule a technician, or send project documents for a written proposal.