Experimental Study on Mechanical and Thermal Properties of Backfill Body with Paraffin Added

Based on phase-change heat storage backfill, paraffin microcapsules were selected as the phase change material and were directly mixed with backfill materials for preparing backfill specimens. The mechanical and thermal properties of specimens with different paraffin percentages and slurry concentrations were tested and analyzed. The results show that compressive strength gradually decreases with an increasing paraffin percentage while it significantly increases with increasing slurry concentration, thermal conductivity decreases with increasing paraffin percentage and specific heat capacity increases with an increasing paraffin percentage and slurry concentration. For a paraffin percentage from 0% to 10%, compressive strength decreases by an average of 22.5%, thermal conductivity decreases by an average of 43.8% and specific heat capacity increases by an average of 8.7% at a phase-change temperature of 30 °C. For a slurry concentration from 68% to 72%, compressive strength increases by an average of 4.12 times, and specific heat capacity increases by an average of 3.5% at a phase-change temperature of 30 °C. The weakening effect of phase-change materials on compressive strength can be effectively improved by the increase of slurry concentration, and the increases of paraffin percentage and slurry concentration can both improve the sensible heat storage capacity of backfill materials.