Abstract
Shear stress of sericite suspensions was measured against shear rate in the range of 16 to 650s-1 using a rotational viscometer. Mineral compositions of two kinds of clay particles (AT-S, AT-K), which were obtained by elutriation from two different kinds of powdered Amakusa pottery stones, were mainly sericite and a few amount of kaolin mineral and quartz. Rheological properties of these sericite suspensions were approximated as Bingham body and analysed using DLVO theory of coagulation and dispersion. The results were summarized as follows;
(1) Bingham yield stress (BYS) values obtained from the relation between shear stress and shear rate became higher with increasing the volume fractions of AT-S and AT-K suspensions from 1.8% to 6.9%. BYS values of two suspensions were nearly zero at pH 7, increased from pH 6 to pH 5, and decreased at pH 4.
(2) Total potential energy of interaction between two flat clay particles and Bingham yield stress (BYS) of clay suspensions were calculated using the estimated edge and face potentials of sericite on the basis of DLVO theory and the equation of total energy dissipation rate. The calculated results showed that BYS values of both sericite suspensions became zero at pH 7, then had finite values at pH 6 and pH 4, and had a maximum at pH 5 because these calculated values were brought about from the different association modes such as face to edge and edge to edge. These changes of calculated BYS values with pH explained well those of measured ones. It was also made clear that the thickness of sericite gave a great effect on BYS values.
