Determination of the reactivity of clay-fluid systems using liquid limit data

The reactivity coefficient, defined as lambda = rho(w)G(s)S(a)theta(rho(w) is the mass density of water, G(s) is the specific gravity, S-a is the spec ific surface, and theta is the double-layer thickness), has been proposed a s a parameter to assess the sensitivity of a clay-fluid system to changes i n physical and chemical properties of the pore fluid. In this study, the li quid limit of a clay-fluid mixture, w(L), is shown to be related to the rea ctivity coefficient. Double-layer theory is applied to determine the void r atio at the liquid limit, which is assumed to occur at a stress close to 10 kPa. Liquid limit data were measured for a bentonite clay at different por e-fluid concentrations; other data were collected from the literature. Both measured and collected data followed the proposed simple expression, sugge sting that then is a unique relationship between w(L) and lambda, at least for the three-layer sheet minerals (or for clays with w(L) > 50). The propo sed expression can be used as a simple approach to determine the sensitivit y of clay-fluid systems. A parametric study based on the lambda-w(L) relati onship is presented to study the effects of temperature and pore-fluid conc entration on the liquid limit.