Flexural Fatigue Durability of Selected Unreinforced Structural Lightweight Concretes: Fid-Bau Portal

Flexural Fatigue Durability of Selected Unreinforced Structural Lightweight Concretes

J. C. Chakrabarti / W. B. Ledbetter

In the research study, the fatigue durability of concrete was reviewed, a reproducible flexural fatigue test was developed, and the flexural fatigue durability of selected unreinforced structural lightweight concretes was determined. Also, relationships between flexural fatigue durability and freeze-thaw durability of selected concretes were established. Fatigue tests were conducted on unreinforced prisms of three lightweight concretes and one regular weight concrete. Two of the lightweight concretes and the regular weight concrete were tested in a moist condition, and one lightweight concrete was tested in a dry condition. In the fatigue tests, all specimens were subjected to repeated sinusoidal stress cycles at the rate of 697 cpm. The fatigue stress levels were determined as a percentage moduli of rupture of identical prisms. All concretes were cured for a minimum period of 28 days prior to testing. Following are the important conclusions that were derived from this research: The resistance of unreinforced structural concrete to flexural repeated load was dependent on the applied stress amplitude, the variation of the log of the fatigue life being inversely proportional to the applied stress up to 10 million repetitions of the load for all the concretes tested. Type of coarse lightweight aggregate definitely affected the flexural fatigue behavior of unreinforced structural concrete. Dry concrete exhibited longer fatigue life than wet concrete. A relationship was found to exist between fatigue durability and freeze-thaw durability for the conditions of this study. (Author)