Effect of hydration at various temperatures on the thermal conductivity of compacted Indian bentonites

• Thermal conductivity of bentonites with hydration at various temperatures are highlighted. • Thermal conductivity of compacted bentonites is influenced by pore volume fractions. • Thermal conductivity of bentonites increases with temperature, related to water content. • Inter-aggregate pores within compacted bentonites decrease with temperature. Thermal conductivity of bentonite is one of the key parameters influencing thermal behavior of geological repositories, where bentonite can serve as a buffer material. ​This study experimentally investigated the effects of hydration period with temperature (27℃→80℃→100℃→120℃) on the thermal conductivity of bentonites, compacted with varying water content and dry density. It was observed that thermal conductivity increased with hydration period at 27℃ for specimens with lower water content, whereas it decreased for those with higher water content for given dry density. However, it increases with temperature, increased significantly during early hydration period and tended slow rate increase after 5 days of hydration for temperatures above 80℃. The change in thermal conductivity with temperature during hydration was minimal for dry specimens, whereas it changed significantly in specimens with higher water content. Hydration of compacted bentonites with various temperatures decreased inter-aggregate pore fractions, increasing particle contact area, confirmed by microstructure investigations.