CRACK-PROPAGATION IN CONCRETE SUBJECTED TO FLEXURAL-CYCLIC LOADING

Fatigue tests were carried out on notched micro-concrete beams subject ed to three-point bending tests in a saturated atmosphere. The feature of the crack growth was studied by means of the replica technique ass ociated with scanning electron microscopy, in conjunction with the mea surement of the crack mouth opening displacement (CMOD). Two domains m ust be distinguished in which the fatigue can be considered, depending on the upper boundary of the cyclic load. Beyond a given threshold fo r the upper boundary of the cyclic load, the first cycle induces an ac tual crack at the tip of the artificial notch. Observations of fatigue crack propagation are presented in that case and compared with previo us investigations in static tests. The influence of the load level on the crack growth rate is discussed.