Flexural Residual Strength of Lightweight Concrete Reinforced with Micro-Steel Fibers

초록

The objective of the present study is to assess the flexural residual strengths of lightweight aggregate concrete (LWAC) reinforced with micro -steel fibers. Further, the material class of such concrete was examined through comparison with the fiber -reinforced concrete classification specified in the provisions of fib 2010. Fourteen beam specimens were classified into L (21 MPa [3.05 ksi]) and H (40 MPa [5.80 ksi]) groups according to the design compressive strength of LWAC. The volume fraction of micro -steel fibers varied from 0 to 1.5% at a spacing of 0.25% in each beam group. From the beam test results under the three-point loading condition, flexural stress -crack mouth opening displacement (CMOD) curves were measured and then discussed as a function of the fiber reinforcing index (beta f). The flexural residual strengths corresponding to four different CMOD values (0.5, 1.5, 2.5, and 3.5 mm [0.02, 0.06, 0.1, and 0.14 in.]) were compared with previous empirical equations and fib 2010 classification. The various analyses of the measured results indicate that beta f can be regarded as a critical factor in directly determining the magnitude of flexural residual strengths and assessing material classification. The proposed refined equations improve the accuracy in predicting the flexural residual strengths of concrete beams with different densities and reinforced with different types of steel fibers. Consequently, microsteel fibers are a promising partial replacement for conventional steel reinforcing bars to enhance the ductility of LWAC elements.

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