Mechanical and microstructural properties of heated and polluted kaolinite and bentonite

Abstract

High temperatures and pollution due to the storage of nuclear wastes in deep soil influence the mechanical properties and microstructure of kaolinite and bentonite. In this study, 0.5 N CaCl2 and 2000 ppm ZnCl2 solutions were added to kaolinite(k) and bentonite(b) samples treated at different temperatures ranging between 100 and 600degreesC. After the preparation of the samples, particle size variation, consistency limits and unconfined compressive strength values of the clays were calculated by means of standard experiments. In addition, the pH level, electrical conductivity, salt and metal pollution of the samples were determined. Microstructural properties of the samples were analyzed by means of SEM. Experimental results revealed that heating and polluting the clays at 600degreesC decreased the clay size fraction, the liquid limit and the plastic limit but increased the silt size fraction and unconfined compressive strength values. According to electrical conductivity (EC) values, the samples that contained ZnCl2 were natural clays, whereas those that included CaCl2 were saline clays. This work establishes the advantages of observing mechanical properties parallel with microstructure variations in order to understand the changes in the properties of clays.