Shotcrete thermal insulation technology is an effective measure to prevent heat transfer from high-temperature surrounding rock to the roadway. Incorporating porous heat-insulating materials can enhance the thermal insulation performance of shotcrete, however, this may result in a reduction of its mechanical strength. This study investigated the relationship between the ratios of porous materials and both mechanical strength and thermal conductivity. A novel type of thermal insulating shotcrete was developed by using floating beads, vitrified microbeads, and porous shale ceramic particles as partial substitutes for aggregates and cementitious materials. Orthogonal experiments were conducted to analyze the variations in compressive strength, splitting strength, and thermal conductivity of this material at different curing ages. XRD experiments were employed to examine the interactions among the insulation materials, leading to the determination of the optimal ratios of various insulating components. The results indicated that when the proportions of floating beads, vitrified microbeads, and ceramic particles were 7.5%, 1.5%, and 30%, respectively, the insulated shotcrete demonstrated excellent thermal properties with minimal loss of compressive and splitting strengths, thereby satisfying the requirements for both thermal insulation and structural support. Furthermore, a thermal insulation and heat transfer model for insulated shotcrete containing multi-level pore size materials was proposed. This study offers a novel approach to enhancing the thermal insulation performance of shotcrete.
Chen et al. (Fri,) studied this question.