This recommended practice describes a procedure for classifying soils into seven groups based on
laboratory determination of particle-size distribution, liquid limit, and plasticity index. Evaluation
AASHTO M 145-1991 history
1970AASHTO M 145-2017 Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes
1991AASHTO M 145-1991 Standard Specification for Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes