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One of the commonly used stabilization systems for rock tunnel is shotcrete. However, the hydration of shotcrete is usually accompanied by the development of internal defects and micro damage under high temperature. Additionally, in the actual high‐temperature engineering, the temperature of the rock tunnel exhibits irregular changes. Therefore, in this study, the curing conditions of constant temperature (23°C, 40°C, 60°C, 80°C) and variable temperature (23–40–60–80°C, 80–60–40–23°C) are set, respectively. The mechanical properties and structural properties of polyurethane shotcrete and ordinary Portland shotcrete are introduced. It is determined that the limit temperature for inhibiting the development of sprayed concrete's compressive and splitting strength is between 60°C and 80°C, and the limit temperature for inhibiting the development of bond strength is about 40°C. Meanwhile, the influence of high temperature on the thermal insulation performance of shotcrete is considered. The results that the self‐foaming performance of polymer(polyurethane) reduces the thermal conductivity of shotcrete. Based on this phenomenon, the heat transfer model of shotcrete at room and high temperature is established to clarify the heat transfer process of shotcrete. Results will provide theoretical basis for further research of durability and heat insulation performance of protective spraying material for tunnel under high temperature. [ABSTRACT FROM AUTHOR]

The procedure of numerical identification of thermophysical properties of concrete during its hardening is presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The developed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of direct search optimization algorithm. The determined thermal characteristics of concrete are not constant and depend on the maturity of concrete. The procedure was verified on set of concrete mixes designed with Portland cement CEM I 42.5R and Portland-slag cement CEM II/B-S 32.5 N. Calcareous fly ash was also used for partial replacement of cement in the mixtures. The obtained results have been compared with experimentally measured temperature in concrete and a fair agreement has been found. [ABSTRACT FROM AUTHOR]