Soil Modification is sometimes referred to as "mud drying;" however, soil modification can result in other significant improvements in soil properties as well. Often, subgrade soils are too wet, exhibiting poor workability and lacking sufficient strength to support construction equipment. Chemical additives such as lime, fly ash, and cement can be added to these soils to dry and improve the workability of the soil.

Soil modification refers to the process of adding and mixing the above chemical agents into the soil to not only dry the soil, improving workability, but also reducing the plasticity index (PI) and shrink swell potential. These improvements often result in a slight increase in the shear strength of the soil.

There are two types of Soil Stabilization, chemical and bituminous. Chemical stabilization is the process of adding and mixing additional amounts of the same chemical agents used in soil modification into the soil to allow a significant increase in strength of the soil, thus improving the load bearing capacity of a sub-grade to support pavements and foundations. Soil stabilization results in the same improvements in soil properties that are achied with soil modification. Bituminous soil stabilization results in an improvement is soil strength but is not generally recommended for clay soils; therefore, is not used to modify soils. Many agencies require a specified increase in unconfined compressive strength before a soil can be considered a stabilized layer.