THERMAL CONDUCTIVITY OF OTTAWA SAND PARTIALLY AND TOTALLY SATURATED WITH WATER

Ottawa sand is a widely studied material in as much its properties are well known, and so it is particularly suited to be used as reference material to develop new analysis methods. This is the reason why it has been chosen to investigate thermal conductivity of partially saturated with water porous media with the probe method. To this goal a special probe developed by the authors’ laboratory has been used, whose accuracy had been established during previous tests as 1.5 %. Thermal conductivity of Ottawa sand has been measured in three different states: dry, totally saturated with water, and saturated to 50%. In all conditions values were measured as a function of temperature from –20 °C to 80°C. A special procedure has been studied and tested in order to get best uniformity of water distribution in the material. Many measurements have been repeated supplying different electric power to the probe, in order to vary the temperature increase. The aim of this action is to recognize a possible influence of phase change, due to the power supplied for the test procedure itself, during measurements. Results show a typical behaviour of thermal conductivity versus temperature, intermediate between the solid phase and fluid one. Also a characteristic behaviour versus temperature increase is evident in single tests, due to different phenomena occurred in the three phases porous media.