Hydromechanical Characterization of Cement-Bentonite Slurries in the Context of Cutoff Wall Applications

Abstract

In the one-phase construction of cutoff walls, the slurry plays two contradictory roles: it should be fluid while excavating the trench but behave like a solid of low permeability afterward. For hydraulic containment applications, a mixture of water, cement, and bentonite fulfils these requirements, but the range of mix proportions is very limited. In the past, this discouraged systematic research on the subject, and, in consequence, a certain empiricism still prevails in the definition of the slurry composition. This paper presents the results of an extensive experimental program, which is part of a broader investigation regarding the technology of self-hardening slurry walls. Referring to triaxial tests, the stress-strain behavior and permeability of cement-bentonite slurries fabricated and cured in the laboratory is characterized. A conceptual microstructure model is proposed to explain the slurry’s behavior in light of the chemical reactions between its constituents. The final objective is to establish a relationship between the behavior of lab-made slurry and that of in situ slurry, and consequently to be able to predict the long-term behavior of the wall.