Purpose of AASHTO Soil Classification System

• The classification system was originally developed in 1929 as paved roads and highways began to take form and become more abundant. Soil had to support the weight of paved roads. At the time, there was not much knowledge concerning the types of soil suitable for holding the weight of a paved road, so building paved roads or surfaces could be difficult. Classifying soil and soil mixtures provided highway construction planners with a way to plan upcoming projects.