Abstract: Recognition of the fact that clays exhibit both viscous and elastic response characteristics has led to the use of the theory of viscoelasticity for describing their mechanical behavior. This paper presents a brief outline of pertinent concepts from this theory to establish a framework for the presentation and interpretation of the experimental results. The experimental program was conducted on a water-washed Georgia kaolin at nominal moisture contents of 50%, 75%, and 100%, and included a series of oscillatory shear tests over a frequency range of two decades. These tests were performed on a Weissenberg Rheogoniometer with a cone-and-plate sample holder; this arrangement produces essentially homogeneous shear strains throughout the specimen.
The experimental results show that the stress-strain response of the clay is frequency-dependent and is definitely nonlinear, even at small strains. The greatest frequency dependence, as manifested in the complex shear modulus and phase angle, occurs in a region characteristic of many polymer systems. The logarithm of the complex shear modulus is found to vary approximately as the water content or consistency of the clay-water mixture.