What does the AASHTO Classification System take into account for soil classification?

The AASHTO Classification System, which is utilized for classifying soils primarily for highway and airfield construction, incorporates important factors that influence soil behavior and engineering properties. The key components taken into account in this system include sieve analysis, liquid limit, and plasticity index.

Sieve analysis helps determine the distribution of different particle sizes within the soil, which has a substantial impact on the soil's drainage characteristics and compaction behavior. The liquid limit reflects the moisture content at which the soil transitions from a plastic to a liquid state, indicating its ability to deform under stress. The plasticity index, which is derived from the difference between the liquid limit and the plastic limit, provides insights into the range of moisture content over which the soil remains plastic, helping to assess its workability and stability.

Together, these parameters allow civil engineers to classify soils in a way that relates to their suitability for construction purposes, helping guide decisions related to material selection, design, and construction methods. This multidimensional approach makes the AASHTO Classification System robust and effective for predicting soil behavior, rather than relying solely on any one characteristic like particle size, shear strength, or compressive strength in isolation.