---
title: "AASHTO Soil Classification System"
chunk: 1/1
source: "https://en.wikipedia.org/wiki/AASHTO_Soil_Classification_System"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T09:08:40.762171+00:00"
instance: "kb-cron"
---

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, but has been revised several times since.

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 ==


== See also ==
Unified Soil Classification System