RESEARCH ON THE COMPRESSIVE FATIGUE PROPERTIES OF HIGH STRENGTH CONCRETE AFTER HIGH TEMPERATURE

Fatigue tests are performed on 100 mm×100 mm×100 mm cubic specimens of plain high-strength concrete (HSC, 60 MPa) subjected to compression cyclic loading using aelectro-hydraulic servo fatigue testing machine. The effects of 100℃, 400℃ and 700℃ on the compressive strength, fatigue strain, residual strain, fatigue deformation modulus, fatigue life and so on are studied. The results show that the color of HSC becomes shallow after high temperature process, i.e., the test block is rust and red after 1h with 400℃ constant temperature, and the appearance of the test piece is gray at 700℃. Under the uniaxial compression fatigue load, the residual strain of concrete is in accordance with the three-stage development law, and the second stage is longer than that of the ordinary concrete. The relative residual strain is defined as the damage variable, and the relationship between the high temperature process and the fatigue damage is established. The results will be useful for the fatigue damage analysis of HSC subjected to comprehensive working conditions with repeated loading and different high temperature process.