Soil Modification by Admixtures: Concepts and Field Applications

Civil engineering construction projects, particularly highway projects, built on problematic soils, including soft soils, expansive soils, and other soil types, require some form of soil stabilization to improve the subsoil properties. Without the stabilization, the infrastructure will experience severe distress, which results in poor performance.Throughout the years, several studies have been conducted to address the performance of soil stabilization methods and construction practices. These stabilization practices can be broadly classified into four main categories of methods based on soil improvement processing mechanisms: mechanical stabilization, chemical stabilization, thermal stabilization, and electrical stabilization. Among these, chemical additives are most often used to stabilize the soils by enhancing their inherent properties. Stabilization through chemical additives, such as lime, cement, and fly ash, modifies the soil properties, resulting in a stronger foundation-supporting infrastructure. This chapter primarily discusses the chemical treatment methods used in practice to stabilize subsoils.A wide variety of chemical additive treatment methods, including lime, cement, fly ash, and other ashes, and ground granulated blast furnace slag are discussed in this chapter. The design of the stabilizers and the appropriate dosages to enhance soil properties to certain prescribed levels, as well as the laboratory mix design methodologies, are discussed. Field construction practices, along with quality control and assessments followed, are also mentioned. At the conclusion of the chapter, a summary of the field application methods and the performance of different stabilizers is presented.