The cuboid method for measurement of thermal properties of cement-based materials using the guarded heat flow meter

Contact resistance can significantly affect the measurement of thermal conductivity of cement-based specimens using contact methods. A new method is proposed which has a reduced time and material requirement compared with the currently accepted methods: the Cuboid method. The Cuboid method requires just one cuboid-shaped sample of relatively small contact area, surrounded by insulation board, while the currently accepted two-thickness and multi-thickness methods require at least two samples of contact area greater than the metering area of the apparatus. Results from the Cuboid method and multi-thickness method were compared for specimens of Polymethyl methacrylate (PMMA) acrylic and hydrated CEM II Portland cement paste. The results differed by just 3.6% and 7.7% respectively for thermal conductivity measured in steady state condition. A non-steady-state method for the determination of specific heat capacity and thermal diffusivity of cement-based specimens, developed from the Cuboid method, is also presented. Relative uncertainties of the results for cement pastes measured in steady-state and non-steady state condition ranged from 2.2 to 11.5%.