Cohesion, Adhesion, and the Durability of Stabilized Materials

Abstract

Stabilization projects have been implemented in various parts of the world to improve the strength and bearing capacity of foundations and to control the permeability, shrink–swell potential, and related characteristics of soil materials. A primary stabilization method is using amendments that have textural, mineralogical, and chemical characteristics that are capable of generating the required changes in physicochemical characteristics of soils when they are mixed. Stabilization agents that are currently available for soil improvement include portland cement, bituminous cement, fly ash, slags, lime, lignins, calcium salts, and polymers. The composite materials formed through soil stabilization vary in degree of cementation from free particles to monoliths in which soil and other introduced particles are bound. Whatever the degree of cementation attained, pores within particles intragranular pores and pores among particles intergranular pores cannot be completely eliminated from stabilized materials. Invariably, solid–solid, solid–liquid, solid–air, liquid–air, and triple interfaces exist in stabilized materials. These interfaces are the primary locations of physicochemical and biological processes that have significant implications on the initial strength and durability of stabilized materials. Across solid–solid interfaces, particles may be of the same or different materials, the statistics of which depend on the mix proportions of the host material often, a multicomponent soil and the stabilization agent, if it is initially in solid form. Usually, the agent is applied in the liquid form, but regardless, subsequent precipitation of new solid phases derived from substances in the agent as well as in the host material, can still create new solid– solid interfaces. Obviously, the prominence of interfaces involving liquids and air depends on the porosity and permeability of the stabilized material and pore fluid chemistry. Interfaces are weak links in materials, because they provide greater opportunities than intact portions of materials for stress concentrations through a variety of mechanochemical processes. These mechanisms and processes are briefly discussed herein, with respect to the durability of chemically stabilized geomaterials. The surficial environment typically, 0–10 m deep in which field stabilization projects are usually performed is subjected to cyclical stresses and reversals of environmental conditions over hours, days, and months. Within the bounds of the microclimate of the region of concern, daily and seasonal reversals in ground temperature, as well as moisture conditions, occur. As a result of contaminant emissions from industrial and civil facilities and con-