DETERMINATION OF THERMAL-DIFFUSIVITY OF CONSTRUCTION MATERIALS

This paper describes a simple and rapid laboratory method for the measurement of the thermal diffusivity of construction materials by heat conduction in short cylindrical specimens. The technique is relatively simple and requires only the measurement of the temperature history at the midpoint of the specimen during heating and cooling in a constant thermal bath using an imbedded thermocouple. A unique theoretical solution is produced for transient heat conduction in a short cylinder which permits the deduction of the thermal diffusivity by curve fitting the experimental data to the theoretical curve. The solution takes into account the variation of cylinder heights and is specialized for specimens of 100 mm fixed diameter and conductivities in the range of 0.5 to 3.0 W/m.K. This solution is commonly applicable to construction materials such as asphaltic concrete, portland cement concrete, portland cement, and brick. Diffusivity is determined by a three-point fitting between experimental data and theoretical solution that verifies the consistency of the value obtained. Experiments for three types of materials, namely, asphaltic concrete, portland cement concrete, and hardened portland cement, are performed to validate the procedure.