Soil Improvement Using Lime and Fly Ash

Using Lime and Fly Ash for Soil Stabilization

Lime Stabilization of Clay Soils

Lime is an economical method for stabilizing clay soils. The appropriate lime concentration is selected based on the target pH. If the lime content is insufficient, it will not provide the required strength or durability.

Lime is typically used in 5% to 10% concentrations and can be mixed in-place or injected as slurry. The effectiveness of soil stabilization in excavations (retaining walls, nailing, anchoring, top-down, etc.) depends heavily on the chemical reaction between the lime and clay.

During this reaction, monovalent cations in clay are usually replaced by divalent ions, causing clay particles to grow in size and improving soil strength.

Fly Ash for Soil Stabilization in Excavations

Fly ash, a byproduct of coal combustion, is increasingly used to stabilize soils. Though it has weaker cementitious properties than cement or lime, it is classified as a secondary binder.

Fly ash alone is not effective in stabilizing clay soils in excavation projects (nailing, anchors, micropiles, top-down, etc.). Therefore, it must be used in combination with lime or cement to ensure effective stabilization.