Evolution of High Toughness Cementitious Composites Gas Permeability after Thermal-Mechanical Coupling Damage

High-toughness cementitious composite (HTCC) may be considered for use as a concrete lining material for underground lined rock caverns in compressed air energy storage (CAES) power stations. This experiment investigated the effect of coupled thermal-mechanical cycling on the changes in the gas permeability and pore structure of HTCC. According to the different operating conditions of CAES power stations, nine test conditions were selected with a compressive stress of 10 MPa and a temperature of 150 °C. The test results show that the HTCC have a peak tensile strain of up to 1.6% and an average crack width of 41~49 μm, providing good toughness and crack control. The permeabilities of HTCC were all significantly larger after loading by thermal-mechanical coupling cycles, but the change in permeability was more sensitive to compressive stresses. When the compressive stress is lower than 7.5 MPa and the temperature is lower than 100 °C, the permeability of HTCC can be maintained within 10−18 m2 orders of magnitude after the thermal-mechanical coupling cycle, which can satisfy the requirement of CAES impermeability performance. When the compressive stress reaches 10 MPa, the HTCC’s critical pore size increases, the pore size coarsens, and the permeability resistance deteriorates rapidly.

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