Abstract
Compressive fatigue strength of concrete under the water is known to drop considerably, but the reason has not yet been cleared. The fracture process of concrete is the generation and propagation process of internal microcracks. Considering that forming each microcrack requires surface energy which is reduced by surface tension of water, the deterioration of fatigue strength of concrete under the water is likely to be explained as the decreasing of surface energy. In this study, compressive fatigue strength of concrete was investigated from the perspective of surface energy. It became clear that K value in Goodman-type S-N curve equation decreased linearly with increasing surface tension of liquid saturating internal void of specimen. It was also indicated that when a static strength of concrete saturated with water was set as the standard value of stress ratios, sufficient attention should be paid to the fatigue strength of concrete saturated with liquids with higher surface tension than water while it hardly mattered in the air.
