INVESTIGATION ON FAILURE CRITERION OF AIR-ENTRAINED CONCRETE UNDER BIAXIAL LOADS AFTER FREEZE-THAW CYCLES

The strength experiments of air-entrained concrete after 0, 100, 200, 300 and 400 freeze-thaw cycles under biaxial compression and biaxial tension-compression are carried out. The failure characteristic of specimens and the direction of surface cracking are observed. The influences of freeze-thaw cycles and stress ratio on the ultimate compressive and tensile strength are analyzed. The failure criterion expressed in terms of principal stress after different freeze-thaw cycles and stress ratios for specimen under biaxial loads is proposed. In addition, the failure criterion under biaxial compression with consideration of the influence of freeze-thaw cycles and stress ratio is proposed. The failure criterion under biaxial tension-compression with consideration of the influence of stress ratio is established in octahedral stress space. The experimental and theoretical foundations for strength analysis of air-entrained concrete structures subject to biaxial loads in cold environment are provided.