Triaxial compressive strength experiment study of recycled aggregate concrete after high temperatures

To study the triaxial compressive properties of recycled aggregate concrete (RAC) after high temperature, 100 Ф100 mm × 200 mm cylindrical RAC specimens with different replacement rate (0%, 30%, 70%, 100%) were fabricated to the conventional triaxial experiment (with the lateral confining stress of 0 MPa, 5 MPa, 10 MPa, 15 MPa and 20 MPa) after exposure to different high temperatures (20 °C, 200 °C, 300 °C, 400 °C, 500 °C). The results show that the specimens present longitudinal splitting failure form when under uniaxial stress condition and inclined plane shear or flake splitting failure form when under triaxial stress condition. The triaxial compressive strength presents the trend of decreasing → increasing → decreasing with the increase of replacement rate. Improving lateral confining stress can effectively improve the compressive strength of RAC. The triaxial strength of specimens is almost equal to each other when the temperatures do not exceed 400 °C. After 500 °C high temperature, the triaxial strength will gradually decrease, but the decrease amplitude is far less than that of uniaxial strength. Based on test data and some related theories, the triaxial strength calculation formula of RAC with different replacement rate after high temperatures was given. And it can provide some references for the related research and practical engineering application of RAC.