AASHTO Soil Classification System
{{Short description|Classification of soils for road-construction purposes}}
The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes. The classification system was first developed by Hogentogler and Terzaghi in 1929,{{cite journal |last=Hogentogler |first=C.A. |author2=Terzaghi, K. |title=Interrelationship of load, road and subgrade |journal=Public Roads |date=May 1929 |pages=37–64}} but has been revised several times since.
| class="wikitable"
|+ AASHTO Soil Classification System (from AASHTO M 145 or ASTM D3282) |
| General Classification
! colspan="7" | Granular Materials (35% or less passing the 0.075 mm (No. 200) sieve) ! colspan="4" | Silt-Clay Materials (>35% passing the 0.075 mm (No. 200) sieve) |
|---|
| rowspan="2" | Group Classification
| colspan="2" | A-1 | rowspan="2" | A-3 | colspan="4" | A-2 | rowspan="2" | A-4 | rowspan="2" | A-5 | rowspan="2" | 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, % passing
| colspan="11" | |
| 2.00 mm (No. 10)
| 50 max | … | … | … | … | … | … | … | … | … | … |
| 0.4255 mm (No. 40)
| 30 max | 50 max | 51 min | … | … | … | … | … | … | … | … |
| 0.0755 mm (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 0.425 mm (No. 40)
| colspan="11" | |
| Liquid Limit
| colspan="2" | … | … | 40 max | 41 min | 40 max | 41 min | 40 max | 41 min | 40 max | 41 min |
| Plasticity index
| colspan="2" | 6 max | N.P. | 10 max | 10 max | 11 min | 11 min | 10 max | 10 max | 11 min | 11 min1 |
| Usual types of significant constituent materials
| colspan="2" | stone fragments, gravel and sand | fine sand | colspan="4" | silty or clayey gravel and sand | colspan="2" | silty soils | colspan="2" | clayey soils |
| General rating as a subgrade
| colspan="7" | excellent to good | colspan="4" | fair to poor |
Plasticity index of A-7-5 subgroup is equal to or less than the LL - 30. Plasticity index of A-7-6 subgroup is greater than LL - 30.
References
{{reflist}}
See also
{{Soil type}}
{{DEFAULTSORT:Aashto Soil Classification System}}