THE MEASUREMENT OF THE THERMAL-CONDUCTIVITY OF SOLID AGGREGATES USINGTHE TRANSIENT PLANE SOURCE TECHNIQUE

In predicting the overall thermal conductivity of composite porous str uctures such as building materials or soils, the thermal conductivitie s of their solid components must be known in order to apply some theor etical models. Horai proposed a method to determine the thermal conduc tivity of solid particles. The material under study is first ground to a fine powder. This powder is then carefully saturated with a fluid a nd the thermal conductivity of this mixture is measured using the 'nee dle probe' method. Finally, the conductivity of the solid phase is eva luated using a mixing-law model, namely the mean of the so-called 'Has hin and Shtrikman bounds'. We have introduced a slightly different ver sion of this method that uses the 'transient plane source' (TPS) techn ique recently developed by Gustafsson for simultaneously measuring bot h the thermal conductivity and the thermal diffusivity of solids or fl uids. An adapted experimental device has been designed and our approac h has been validated through measuring, at room temperature, the therm al conductivities of the well-known minerals quartz, calcite and kaoli nite. Afterwards, while considering that our method had become fully o perational, we studied the thermal conductivity of the solid aggregate s of a light-weight, energy-saving concrete whose solid phase is a mix ture of natural clay, hardened cement paste and wood aggregates in var ious proportions.