Durability of Fiber-Reinforced Concrete Under Flexural Stress in a Severe Marine Environment

摘要

In July 1975, the U.S. Army Engineer Research and Development Center (ERDC), initiated a long-term durability study of fiber-reinforced concrete exposed to a severe marine environment. Fifty concrete beams were constructed that were reinforced with various types and sizes of distributed fibers available on the market at the time (carbon-steel, stainless steel, and glass). The beams were then placed at midtide elevation on the exposure wharf at the ERDC Severe Weather Exposure Station, Treat Island, Maine. Sixteen of the beams were yoked and stressed to 35 percent of their flexural strength with third-point loading. In 1993 there were twelve stressed beams which had survived 18 years of severe marine exposure. These were removed from exposure and subjected to a wide variety of destructive and nondestructive experiments under laboratory conditions. This report documents the investigation to determine the material properties of the fiber-reinforced concretes and evaluate the beams in their as-removed condition documenting flexural strength, toughness and the effect of stress direction. The report also investigates material properties of the beams by use of a scanning electron microscope to investigate microstructural and microchemical changes that occurred. Test results document the tensile, compressive, and flexural properties of the beams and show the superiority of carbon-steel-fiber reinforcement over glass fiber, stainless-steel fiber, or no-fiber reinforcement in concrete. Results also indicate that the direction of stress in uncracked fiber-reinforced concrete does not affect its durability and performance in a severe environment.