Thermal Properties of Fly Ashes and Biomass Ashes Including Wood Bagasse Ashes and Sugarcane Bagasse Ashes

Mostly disposed without treatment, fly and biomass ashes have been a challenge that threatens the environment. To use them as geoenvironmental materials for thermal insulating purposes, a fundamental studying of thermal property of the pure ashes is crucial. In this study, thermal conductivities of fly (class C and F) and biomass ashes (sugarcane bagasse and wood) are studied at dry, saturated, and partial saturated conditions under different effective stresses. Moreover, silica sand and kaolinite are used for comparison. The results show that thermal conductivity dramatically increases with effective stress in dry condition, but less increases in saturated condition. Providing partial-saturated conditions, a substantial increase of thermal conductivity is observed with the degree of saturation, which shows a good consistency with an empirical fitting model using thermal conductivities of minerals of dry and saturated materials. Fly ash class C is cemented by reacting with water that causes thermal conductivity to increase by reason of increased particle contact area. Finally, general thermal conductivities of fly and biomass ashes are much lower than both silica sand and kaolinite, which can be considered as insulating materials in geotechnical engineering. (C) 2016 American Society of Civil Engineers.