Characteristics of Geologic Materials and Formations - Geotechnical Engineering Investigation - page 396

TABLE 5.32
American Association of State Highway Officials Classification of Soils and Soil-Aggregate Mixtures AASHO Designation M-145

General Classification a Granular Materials (35% or less passing no. 200) Silt-Clay Material (more than 35% passing no. 200)

Group classification A -1 A -3 A -2 A-4 A-5 A-6 A-7

A-1-a A-1-b A-2-4 A-2-5 A-2-6 A-2-7 A-7-5, A-7-6

Sieve analysis, percent passing:
No. 10 50 max

No. 40 30 max 50 max 51 min

No. 200 15 max 25 max 10 max 35 max 35 max 35 max 35 max 36 min 36 min 36 min 36 min

Characteristics of fraction
passing no. 40:
Liquid limit 40 max 41 min 40 max 41 min 40 max 41 min 40 max 41 min

Plasticity index 6 max NP b 10 max 10 max 11 min 11 min 10 max 10 max 11 min 11 min

Usual types of significant Stone fragments— Fine sand Silty or clayey gravel and sand Silty soils Clayey soils

constituent materials gravel and sand

General rating as subgrade Excellent to Fair to poor

good

a

Classification procedure: With required lest data in mind, proceed from left to right in chart; correct group will be found by process of elimination. The first group from
the left consistent with the test data is the correct classification. The A-7 group is subdivided into A-7-5 or A-7-6 depending on the plastic limit. For w p 30, the classifica-

tion is A-7-6; for w p 30, A-7-5.

b

NP denotes nonplastic.