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Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Deflection-Softening and Deflection-Hardening FRC Composites: Characterization and Modeling
Author(s): A.E. Naaman
Publication: Special Publication
Appears on pages(s): 53-66
Keywords: deflection; deflection hardening; deflection softening; fiber-reinforced concrete; strain hardening; strain softening; polypropylene fibers; steel fibers
Abstract:The load-deflection response of fiber reinforced cement composites generally starts by an initial portion that is linear elastic up to a certain load at which it deviates from linearity; this is often identified as the onset of first cracking in the matrix. If the cement matrix is not reinforced, first cracking is followed by a sudden drop in the load-deflection curve, and failure occurs. The addition of fibers mostly influences the response of the composite after cracking. For all practical purposes, the load-deflection response of fiber reinforced cement composites after first cracking can be simply classified as either "deflection-softening" or "deflection-hardening." This paper describes first the different types of load-deflection curves observed in various experimental tests and illustrates the influence of some fiber reinforcing parameters with steel and polymeric fibers. Then, an analytical formulation is suggested to predict the value of the critical volume fraction of a given fiber to achieve deflection-hardening behavior. Several parameters influence the “deflection-hardening” portion of the curve and include the fiber content, fiber aspect ratio, and fiber to matrix bond.
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