FRACTURE OF CONCRETE SUBJECTED TO CYCLIC AND SUSTAINED LOADING

Sealed specimens of paste and concrete were tested under the maximum cyclic or sustained compressive stresses of 60 to 90% of the ultimate stress. Volumetric strains, ultrasonic velocity and attenuation, and internal microcrack propagation were examined. Sustained or cyclic loading resulted in progressive crack propagation. Crack growth under sustained stresses appeared to result from the phenomenon of stress corrosion while under cyclic loading the process of load repetition played an important role.