Experimental study on thermal and mechanical properties of tailings-based cemented paste backfill with CaCl₂·6H₂O/expanded vermiculite shape stabilized phase change materials

CaCl₂·6H₂O/expanded vermiculite shape stabilized phase change materials (CEV) was prepared by atmospheric impregnation method. Using gold mine tailings as aggregate of cemented paste backfill (CPB) material, the CPB with CEV added was prepared, and the specific heat capacity, thermal conductivity, and uniaxial compressive strength (UCS) of CPB with different cement−tailing ratios and CEV addition ratios were tested, the influence of the above variables on the thermal and mechanical properties of CPB was analyzed. The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl₂·6H₂O is about 60%, and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g, respectively. For the CPB without CEV, the specific heat capacity, thermal conductivity, and UCS decrease with the decrease of cement−tailing ratio. For the CPB with CEV added, with the increase of CEV addition ratio, the specific heat capacity increases significantly, and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74% and 218.97% respectively after adding 12% CEV. However, the addition of CEV leads to the increase of pores, and the thermal conductivity and UCS both decrease with the increase of CEV addition. When cement–tailing ratio is 1:8 and 6%, 9%, and 12% of CEV are added, the 28-days UCS of CPB is less than 1 MPa. Considering the heat storage capacity and cost price of backfill, the recommended proportion scheme of CPB material presents cement−tailing ratio of 1:6 and 12% CEV, and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40°C. This work can provide theoretical basis for the utilization of heat storage backfill in green mines.