# ASTM Aggregate and Soil Terminology

The basic reference for the Unified Soil Classification System is ASTM D 2487. Terms include:

- Canonical URL: https://pavementinteractive.org/reference-desk/materials/aggregate/astm-aggregate-and-soil-terminology/
- Last updated: 2018-07-30
- Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name
- Standards: ASTM D2487

## Terms

The basic reference for the Unified Soil Classification System is ASTM D 2487. Terms include:

- **Coarse-Grained Soils**: More than 50 percent retained on a 0.075 mm (No. 200) sieve
- **Fine-Grained Soils**: 50 percent or more passes a 0.075 mm (No. 200) sieve
- **Gravel**: Material passing a 75-mm (3-inch) sieve and retained on a 4.75-mm (No. 4) sieve.
- **Coarse Gravel**: Material passing a 75-mm (3-inch) sieve and retained on a 19.0-mm (3/4-inch) sieve.
- **Fine Gravel**: Material passing a 19.0-mm (3/4-inch) sieve and retained on a 4.75-mm (No. 4) sieve.
- **Sand**: Material passing a 4.75-mm sieve (No. 4) and retained on a 0.075-mm (No. 200) sieve.
- **Coarse Sand**: Material passing a 4.75-mm sieve (No. 4) and retained on a 2.00-mm (No. 10) sieve.
- **Medium Sand**: Material passing a 2.00-mm sieve (No. 10) and retained on a 0.475-mm (No. 40) sieve.
- **Fine Sand**: Material passing a 0.475-mm (No. 40) sieve and retained on a 0.075-mm (No. 200) sieve.
- **Clay**: Material passing a 0.075-mm (No. 200) that exhibits plasticity, and strength when dry (PI ≥ 4).
- **Silt**: Material passing a 0.075-mm (No. 200) that is non-plastic, and has little strength when dry (PI < 4).
- **Peat**: Soil of vegetable matter.

Note that these definitions are Unified Soil Classification system definitions and are slightly different than [those of AASHTO](https://pavementinteractive.org/aashto-soil-terminology/).