Does anyone know about soil classification?

Specifically Types "A1" through "A7" road bed or sub-grade materials? I need to know how to distinguish between classifications, and cannot find a specification for it.

Public Comments

1. A1 is more gravelly, A7 is clay. Below is the AASHTO system A-1 well graded, essentially non-plastic A-1-a more gravelly (stoney) with or without fine particles A-1-b more sandy with or without fine particles A-3 uniformly graded sand, non-plastic A-2 granular material not being a A1 or A3 material; a distinction is made between: A-2-4 relatively coarse graded mixtures with a substantial amount A-2-5 of fine particles; the fine particles have the properties of a A-2-6 A-4, A-5, A-6 or A-7 soil A-2-7 A-4 loam soil A-5 loam soil containing mica’s; this causes a rather elastic behavior of the soil that makes the soil difficult to compact; this behavior can furthermore lead to cracking in overlying bound layers A-6 clay A-7 clay; a further distinction is made between a A-7-5 and a A-7-6 clay
2. McKinley nailed it. I'd also direct you to the AASHTO (American Association of State Highway Transportation Officials) website or the following chart on Wikipedia: http://en.wikipedia.org/wiki/AASHTO_Soil_Classification_System good luck!