Adsorbed water and its influence on engineering index properties of clays

Abstract

A study was made of the influence of the adsorbed water films on the engineering index properties of clay materials. A review is presented of the available information and knowledge, which was gained from a study pf the related fields of Clay Mineralogy, Soil Physics and Physical Chemistry, for the purpose of explaining to the engineer phenomena commonly observed but not fully understood. Laboratory determinations were made and are reported showing the affect of adsorbed water on the plasticity, consolidation and permeability properties of four specimens of relatively pure clay minerals, namely, kaolinite, illite, sodium saturated montmorillonite and calcium saturated montmorillonite. These determinations were made using both bipolar and non-polar liquids of similar properties. Evaluation of the data shows the affect of the adsorbed water on the above factors. Generally, it was found that the non-polar liquid causes; highly plastic clays to become non-plastic, consolidation characteristics of plastic clays to resemble those for a fine sand and the permeability to increase. X-ray diffraction studies were made to determine the expansion of the sodium montmorillonite with increase in moisture content. The data thus obtained was interpreted and used as a basis for a possible explanation of the significance of the plastic limit, as well as in explaining the consolidation characteristics of a remolded clay specimen. A study was made on the influence of one-dimensional consolidation on the particle orientation. Replicas were made and studied using the electron microscope. The results indicate that the tendency is for parallel orientation of the clay particles in a direction of the applied force.