Colloidal aspects of incompatibility reactions of bentonite with saline leachates as indicated from a modified fluid loss test

Abstract

The fluid loss test has been used by geotechnical engineers for rapid evaluation of the hydraulic barrier properties of bentonites. In this study, a modified fluid loss test, along with viscometric and electrophoretic mobility measurements, was used to assess the colloidal interactions of three powdered sodium bentonites with saline leachates, namely 0–2 N solutions of NaCl and CaCl2. The results indicate that the fluid loss test provides robust and reliable information on the water retention of bentonite; moreover, it gives information on the aggregate structure, size, and settling of bentonite flocs and on the high-salt stabilization phenomena (packing and densification of clay aggregates) in saline leachates. Quantifying the water retention characteristics, along with the colloidal (i.e., flocculation) behaviour, using the fluid loss test, provides detailed understanding of barrier properties of bentonites important for various applications (e.g., barrier systems, dewatering).