Preparation of copper mine tailings-based geopolymers as thermal storage functional backfill materials

The development of geothermal resources in deep mining has garnered extensive research interest in recent years. The present work studies the thermal storage backfill materials synthesized by integrating microencapsulated phase change materials (MPCM) into geopolymers prepared with copper mine tailings (CMT) and blast furnace slag (BFS). With the increment of MPCM content, the compressive strength of the geopolymers declined. Despite this, the lowest 7 days compressive strength of the geopolymers could still reach 24.5 MPa. The results in microstructures of the geopolymers indicated that paraffin was successfully encapsulated within the microcapsules and MPCM was well dispersed in the geopolymer matrix. The melting temperature of the MPCM was 54.78 °C and the melting latent heat was 116.43 J/g. Infrared thermography showed that the highest average temperature of geopolymer with 20 % MPCM was 5.0 °C lower than that without MPCM, indicating superior thermal storage capacity of the geopolymers with MPCM. This study provides a clue for the synthesis of thermal storage backfill materials with in-situ waste in extracting geothermal resources and reducing the temperature of deep mining environments.