Mechanical stabilization is accomplished by mixing or blending soils of two or more gradations to obtain a material meeting the required specification. The soil blending may take place at the construction site, at a central plant, or at a borrow area. The blended material is then spread and compacted to required densities by conventional means.

Generally, smaller amounts of additives are required to alter soil properties, such as gradation, workability, and plasticity, than to improve the strength and durability sufficiently to permit a thickness reduction design. After the additive has been mixed with the soil, spreading and compacting are accomplished by conventional means.

This method requires the addition of chemical agents to the soil to produce the hardened product. There are three main stabilizing agents that can be added, and the method of treatment bears the name of these agents: soil-cement, soil-lime, and lime-fly ash. The methods of chemical stabilization have much in common and involve somewhat similar construction practices. They depend upon hydration, pozzolanic action of lime with silica and alumina, alteration of the clay material, or a combination of these actions. The result is a semirigid, fairly brittle material with considerable compressive strength and moderate flexural strength when tested either statically or dynamicaly. The ultimate strength depends to a great degree on the density that is achieved during compaction and before the mix cures.

Soil stabilization by modification usually results in something less than a thoroughly cemented, hardened or semihardened material. This type of stabilization may be accomplished by compacting, by mechanical blending, by adding cementing materials in small amounts, or by adding chemical modifiers. Cement and lime modifiers (cement-modified soil and lime-modified soil) are used in quantities too small to provide high-strength cementing action. They reduce the plasticity of clay soils. Calcium chloride or sodium chloride is added to the soil to retain moisture (and also control dust), to hold fine material for better compaction, and to reduce frost heave by lowering the freezing point of water in the soil. Bituminous materials, such as cutback asphalts or asphaltic penetrative soil binder (APSB), and certain chemicals, such as polyvinyl acetate emulsion (DCA-70), are used to waterproof the soil surface and to control dust.