Volume 39, Issue 4 (July 2011)
Measurements of Thermal Conduction in Partially Saturated Specimens Using the Transient Hot-Disk Technique
The hot-disk, also known as the transient plane source technique, is used to measure the thermal conductivity of construction materials. The measurements were done at room temperature and under both dry and partially wet conditions. The technique is a transient one, which uses a flat thin sensor (hot-disk), and it has a dual advantage of short measuring time and low temperature rise (around 1°) across the specimen. This advantage prevents a non-uniform moisture distribution that may arise when the temperature difference across a wet test specimen is maintained for a relatively long time. In addition, the flat thin shape of the hot-disk substantially reduces the contact resistance between the specimen and the sensor. More details about this technique will be discussed. The materials consisted of one specimen of common (sand and cement) plaster, one specimen of ground soft soil, and two specimens of soft and hard bricks. A remarkable increase in the mean conductivity values due to the presence of water has been observed, particularly in the soft specimens. The increase is attributed to the increase in water content within the micro-voids (cavities) of the specimens. In other words, the higher the moisture content is, the greater the thermal conductivity will be.