The Role of Fiber Dispersion on Toughness and Deflection Stiffness Properties of SFRCs

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Title: The Role of Fiber Dispersion on Toughness and Deflection Stiffness Properties of SFRCs

Author(s): L. Ferrara, Y.-D. Park, and S.P. Shah

Publication: Special Publication

Volume: 248

Issue:

Appears on pages(s): 83-100

Keywords: fiber dispersion; fresh state behavior; nondestructive monitoring; reinforced concrete; self-consolidating fiber; steel fiber-reinforced concrete; SFRC post-cracking stiffness; SFRC toughness

Date: 9/1/2007

Abstract:
This work presents the results of a research project aimed at assessing the correlation among fresh state behavior mechanical properties in the hardened state and fiber dispersion in steel fiber reinforced concretes. Three fiber reinforced concretes were hence designed and targeted to different levels of fresh state performance: a vibrated concrete, a self consolidating one and a third exhibiting segregation. Fiber reinforcement consisted in all cases of 50 kg/m3 hooked end steel fibers, 35 mm long and with an aspect ratio equal to 65. Square plates 600 mm wide and 60 mm thick were cast for each mix. The dispersion of fibers within the specimens was investigated through Alternate Current Impedance Spectroscopy (AC-IS). Finally, beams were cut from the plates and tested in 4-point bending. From the load-crack-opening and load-deflection response toughness and stiffness parameters were computed to assess the behavior at serviceability and ultimate limit states. The influence of fiber dispersion and orientation in thin plates on the measured mechanical properties is discussed and a correlation is attempted with parameters, such as fiber spacing, suitably defined to represent the dispersion, detected as above. The results clearly highlight the connections existing between fresh state behavior, fiber dispersion and mechanical properties of SFRC, pointing out their importance for a design of the material composition as well as of the casting process "tailored" to the specific structural application.