Aggregation process of kaolinite clay

Clay geomaterials pose a great challenge in geotechnical design due to their complex mechanical behaviour. Despite the vast research on clay mechanical behaviour, mechanisms occurring at the particle-scale still remain largely unknown. Particle-to-particle interactions include electro-chemical forces, which can be in turn associated with repulsive/attractive Coulomb interaction and attractive van der Waals force. This work aims to investigate the role of attractive forces (van der Waals and Coulomb) via their control of the process of aggregation (attractive forces tend to form aggregates of clay particles). Dry clay particles were compressed under high stress to reduce particles distances and activate attractive van der Waals and Coulomb forces. Particle size distribution was then measured using laser granulometry to explore aggregation formation. Laser granulometry tests were performed with and without ultrasound and with and without dispersant. Results show that the higher the compressive stress applied to the sample, the bigger is the ‘particle’ size measured by the laser granulometry, which corresponds to formation of aggregation due to attractive forces. Ultrasound appeared to disaggregate the aggregates thus suggesting that van der Waals and Coulomb forces are sensitive to dynamic loading.