文档介绍：Technician Training and Certification Program
January 2003
Classification of Soil and Soil-Aggregate Mixtures
For Highway Construction Purposes
AASHTO M-145-91 (2000)
(Modified)
This practice describes a procedure for classifying soils into seven groups based on laboratory
determination of particle-size distribution, liquid limit, and plasticity index. The group classification
should be useful in determining the relative quality of the soil material for use in embankments,
subgrades, and backfills. For detailed design of important structures, additional data concerning
strength or performance characteristics of the soil under field conditions will usually be required.
Modification: Determination of Group Index will not be a part of certification, but
taught as a useful tool for more accurate determination of soil
classification.
Key Elements:
1. Determine sieve analysis. Determine sieve analysis using AASHTO T-11 and AASHTO T-27
test procedures (Note 1). The mm (No. 10) sieve, 425-µm (No. 40) sieve, and 75-µm (No.
200) sieve must be included to determine the particle size distribution as a basis for classification.
2. Determine the liquid limit. Determine the liquid limit of the material using AASHTO T-89 test
procedures.
3. Determine the plastic limit. Determine the plastic limit and plasticity index of the m