Experimental Evaluation of Thermal Properties of Grouting Materials

This study is aimed at the thermal analysis of sealant mortar (usually a mixtures of bentonite and cement with addition of sand) used in geothermal cooling and heating. In particular, thermal conductivity and diffusivity measurements were performed on different sealant mixtures by using Hot Disk Thermal Constants Analyser in order to identify the interesting thermal properties of grouting materials. The grouting materials that we considered are of porous nature and, if used in the presence of groundwater, have different levels of imbibitions. It is important to know the thermal behaviour of these materials at different water content. A first set of measurements was performed on a not-tinted material at room temperature; then the samples were led to saturation conditions by contact capillary imbibitions with a cotton wool layer moistened in water. The determination of thermal conductivity in these test conditions appears to be critical compared to the measurements on non-tinted sample. The thermal conductivity tests have revealed how the thermal behaviour of the samples analysed is essentially determined by the density and water content of the material: in fact, the thermal conductivity increases of two to three times the value of the not-tinted material.