Fatigue of Concrete Composed of Blast Furnace Slag or Silica Fume Under submerged condition

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Title: Fatigue of Concrete Composed of Blast Furnace Slag or Silica Fume Under submerged condition

Author(s): Shinobu Ozaki and Noriyuki Sugata

Publication: Special Publication

Volume: 132

Issue:

Appears on pages(s): 1509-1524

Keywords: blast furnace slag; compression tests; fatigue (materials); fatigue tests; pH; silica fume; straining; strength; underwater structures; Materials Research

Date: 5/1/1992

Abstract:
Compressive fatigue strength of concrete in a submerged condition deteriorates drastically compared with concrete in an air-dried condition. One of the reasons for the lowering of fatigue strength in submerged or wet concrete appears to be the influence of the reduction of the bond at the interface between the aggregate and the cement paste. However, this reduction may be mitigated by reducing the calcium hydroxide content and filling the voids at the interface. In this study, compressive fatigue tests were performed in submerged conditions using concrete composed of blast furnace slag or silica fume. The 2-million-cycle fatigue strength of this submerged concrete improved up to 44 percent of its static strength in water compared to 31 percent for ordinary concrete in water. However, this was found to be smaller than 56 percent for ordinary concrete in air. During these tests, the pH of the water in the test tank and the strain of the specimens were measured, and the amounts of calcium hydroxide that oozed out from the specimen and the strain behavior were investigated. The increase in fatigue strength is due to an improvement in the aggregate interface bond and watertightness. However, the expansion of cracks just before failure, which is a distinct characteristic of fatigue in water, was not checked.