Changes in the plasticity of a sample of Champlain clay after selective chemical dissolution to remove amorphous material

Abstract

Although the effect of amorphous compounds on the undisturbed strength of Champlain clay has received much attention, the role of this amorphous material in the behaviour of the sediment following remoulding has been virtually ignored. Selective dissolution procedures on remoulded specimens revealed that removal of up to 4% amorphous material, primarily iron and silicon compounds, was associated with small decreases in specific surface area and cation exchange capacity, and large decreases in liquid limit and plasticity in ex. Analysis of X-ray diffraction traces indicates some alteration of the crystalline components during NaOH–CBD dissolution, but little alteration occurred with the KOH–NH4Ox method, the procedure which achieved maximum extraction of Fe a d Si in this study. It is tentatively concluded that the presence of amorphous material may be responsible for much of the plasticity displayed by Champlain clay rock flour. As a corollary, natural variability in the content of amorphous material in Champlain clay may be correlated with regional and stratigraphic patterns of sensitivity.