Thermal conductivity of cement–based grouts for energy micropiles: Preliminary experimental investigation

Energy micropiles are a kind of energy geostructure designed to reduce the energy consumption of buildings combining structural and thermal performance. Since a common way to improve the thermal efficiency of an energy pile is to increase the thermal conductivity of the concrete (namely, cement, water and aggregate) used in its realization, the same should hold for the mortar (namely, cement plus water) used in the construction of energy micropiles. In this study, the preliminary results of an experimental investigation campaign are presented. The experimental campaign includes thermal conductivity and workability tests carried out on mortar samples and on liquid grouts, respectively. Both neat mortar and mortar plus additives, selected among commercial products with the purpose of increasing the thermal conductivity of the material, were used in the experiments. Three commercial, chemical additives, originally developed for different purposes (e.g., to produce thixothropic mortars, or for the heating floor industry), were used. Experimental results showed that all tested additives were beneficial in increasing the thermal conductivity of the material over the entire range of investigated water/cement ratios, as well as in lowering the initial viscosity of the mixtures. The preliminary results also indicated that one of the tested additives seemed more promising than the others for increasing the thermal conductivity of the hardened grout.