Performance-related characterization of fluidized thermal backfills containing recycled components

The investigation described in this paper focused on the performance-related characterization of cementitious Fluidized Thermal Backfills (FTBs) containing recycled components derived from pavement maintenance and aggregate or stone processing operations. In particular, the study was performed with the purpose of assessing the suitability of these peculiar mixes in situations which require the filling of cavities in the presence of several conduits with high-voltage transmission cables. FTBs were prepared in the laboratory by modifying their standard composition in order to include variable percentages of reclaimed asphalt pavement (RAP) and of three different types of mineral sludge. Components were subjected to preliminary physical characterization and the sludges were investigated in detail with the purpose of identifying their microstructure and chemical composition. In consideration of their intended end-use, FTBs were characterized in terms of their flowability, thermal conductivity and thermal stability. Furthermore, while considering a typical layout of high-voltage cables, an analysis was carried out in order to quantitatively assess the influence of FTB composition and characteristics on line ampacity. Results showed that FTBs may be successfully designed to include recycled components while still retaining satisfactory flow characteristics and thermal properties, although it should be considered that they are extremely sensitive to variations in composition. Furthermore, it was proven that the considered FTBs all led to a satisfactory line ampacity and that in fact their formulation may be adjusted to improve the durability of high-voltage cables.