Geoland Engineering

Epoxy Mortar System: Composition, Mixing, and Application

🔹 AASHTO Soil Classification System👇
👉The AASHTO (American Association of State Highway and Transportation Officials) soil classification system is used to group soils based on their suitability for road and highway construction. It helps engineers determine how well a soil can support pavement and traffic loads. The system divides soils into seven main groups (A-1 to A-7) according to their grain size (how coarse or fine the particles are) and plasticity (how the soil behaves when wet).

👉The A-1 to A-3 groups are called granular soils, meaning they are made mostly of sand and gravel with little fine material (silt or clay). These are considered good to excellent materials for subgrade — the foundation layer of a road.

📍A-1 soils are well-graded sands and gravels, very stable and strong.

📍A-2 soils contain a mix of sand, gravel, and some silt or clay — quality varies depending on plasticity.

📍A-3 soils are fine sands, which can be unstable under traffic or moisture.

📍The A-4 to A-7 groups are silty and clayey soils, which contain more fine particles and generally make poor subgrade materials.

📍A-4 and A-5 are silty soils; A-5 has higher plasticity and holds more water.

📍A-6 and A-7 are clayey soils; A-7 soils, especially A-7-6, are highly plastic and expand or shrink greatly with moisture changes.

👉In simple terms, A-1 soils are the best for road foundations, while A-7 soils are the worst. AASHTO also uses a “Group Index (GI)” number to give a more precise idea of the soil’s performance — a lower GI means better quality.

📝Overall, the AASHTO classification helps engineers choose the right soil for safe, durable, and cost-effective road construction.