Smectite quantification in sediments and soils by thermogravimetric analyses

A new method is assayed, consisting in measuring the weight loss between 100 and 450 °C of samples solvated with ethylene glycol and previously saturated in Mg. This approach allows an approximation to be made of the dioctahedral Al-rich smectite content in samples. The proportion of expandable material in the sample is calculated according to the following equation, obtained from artificial mixtures prepared with variable proportions of smectite: y = 3.96x − 4.05 (R² = 0.96), where x is the percentage of loss and y is the percentage of smectite in the sample. The slope of the equation agrees perfectly with the theoretical proportion of ethylene glycol in a solvated smectite, around 25%, and with the equivalent values determined on natural standards. In addition, the ordinate of the origin is also in agreement with the values of around 1% obtained in smectite-free samples. The method proposed is low-cost and easy to apply as a complement to X-ray diffraction determinations of expandable clay content in sediments and soils with the potential for landslides in civil engineering.