Investigation on the attractive forces controlling clay particles' interactions

Modelling clay behaviour is a challenging task because many of the microscopic features are still unknown including interparticle forces and particle association, which may explain the different behaviours of clay when subjected to hydro-mechanical loading. This paper presents an experimental study to investigate the micromechanical interactions of clay particles. Kaolinite samples were compacted to high vertical stresses and granulometry laser tests were carried out to investigate particle agglomeration. Samples were compacted in a dry state, with 10% water content and 10% dispersant solution content. The results show that loading generated agglomeration. When comparing specimens compacted using different pore fluids, the agglomeration process is more pronounced at high values of dielectric permittivity (water). This study concludes that the association of particles forming agglomerates is due to van der Waals forces. This was mainly inferred from the observation that agglomeration occurred even when compacted samples were prepared with dispersant solution. This also indicates that association of particles occurs in face-to-face mode due to the high stress applied. A similar response of samples compacted with water and sodium hexametaphosphate solution and the environmental scanning electron microscope images of compacted samples also show this type of arrangement. The comprehension of interparticle forces and particle associations can improve discrete modelling of fine-grained materials.