Thermogravimetry and thermodilatometry as auxiliary analyses for dynamical thermomechanical analysis of clays

The natural illitic clay was mixed with powder calcite (22 wt.% in the dry mixture), distilled water, and 3% solution of polyvinyl alcohol to obtain a plastic mass for samples.To determine the correct temperature dependence of Young's modulus, thermogravimetry (TG), thermodilatometry (TDA), and impulse excitation technique (IET) have to be performed in the same temperature regime.The effect of the size of TDA sample on Young's modulus was negligible.Contrary to the TDA sample, the form of the TG sample had a significant effect.When results from a small TG powder sample are substituted into the formula for Young's modulus, relative error up to 10% can result in the temperature region in which changes of some mineral components occur.In this study, we showed the importance of using compact samples with the same cross-section for TG, TDA, and IET in order to obtain correct values of Young's modulus during thermal treatment of the illitic clay.