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TRIS Online Accession Number:00974219
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Edition:Final Report
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Abstract:A comprehensive experimental program on pullout behavior of polypropylene fibers from cementitious matrices is described. The parameters investigated include the effect of embedded length on the pullout characteristics, the development of the interfacial bond with age of curing of matrix and the effect of exposure to degrading environments like seawater and salt water on the interfacial bond between the fibers and cementitious matrix. The aim of these experiments was to understand the properties of fiber/matrix interface, which are of primary significance for the overall behavior of fiber reinforced cement based composites. Polypropylene fibers have a weak bond with cementitious matrix because of smooth surface of fibers, which does not allow for sufficient friction to develop between the two. In this study a new method to improve the frictional bond by means of mechanical indentations of fibers was also proposed. The bonding performance was characterized by means of pullout tests of the plain and modified fibers from a cementitious matrix. An optimum level of fiber modification for maximization of bond efficiency was determined experimentally. Also, recognizing the fact that fibers become most effective only in the post cracking phase of the matrix, a test method called Wedge splitting test was chosen for testing fracture characteristics. This test method allows stable crack propagation, providing valuable information about the post cracking behavior of concrete. Special molds were prepared for making the samples and appropriate fixtures for the experimental setup were fabricated. An experimental scheme to understand the effect of degrading environments on cracked concrete structures was initiated. Wedge splitting tests were used to initiate cracks in concrete samples in a controlled manner. The samples were exposed to salt water to simulate seawater environment. Testing of the control samples has been carried out. The samples exposed to salt water will be tested after one-year exposure. 62 pages.
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