Experimental evaluation of thermal properties of grouting materials

In recent years, the use of techniques of heating and space cooling with ground coupled heat pumps is spreading. This technology, also known as low energy geothermal cooling and heating, plans to use, as a heat source, the subsoil, due to its ability to maintain its temperature constant at values close to the average annual temperature of the locality. The heat exchange with the ground is done by probes that generally consist of U-shaped tubes (single or double) made of plastic and placed in a vertical hole, drilled in the subsoil and filled with grouting materials. For an optimal exploitation of this technology, the use of high thermal conductivity grouting materials is fundamental to minimize thermal resistance and facilitate the heat exchange between the probe and ground. 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 available materials using the so called Hot Disk Thermal Constants Analyser.