Observation of reinforcing fibers in concrete upon bending failure by X-ray computed tomographic imaging
Seok Yong Lim,Kwang Soo Youm,Kwang Yeom Kim,Yong-Hoon Byun,Young K. Ju,Tae Sup Yun
Abstract
This study presents the visually observed behavior of fibers embedded in concrete samples that were subjected to a flexural bending test. Three types of fibers such as macro polypropylene, macro polyethylene, and the hybrid of steel and polyvinyl alcohol were mixed with cement by a designated mix ratio to prepare a total of nine specimens of each. The bending test was conducted by following ASTM C1609 with a net deflection of 2, 4, and 7 mm. The X-ray computed tomography (XCT) was carried out for 7 mm-deflection specimens. The original XCT images were post-processed to denoise the beam-hardening effect. Then, fiber, crack, and void were semi-manually segmented. The hybrid specimen showed the highest toughness compared to the other two types. Debonding based on 2D XCT sliced images was commonly observed for all three groups. The cement matrix near the crack surface often involved partially localized breakage in conjunction with debonding. The pullout was predominant for steel fibers that were partially slipped toward the crack. Crack bridging and rupture were not found presumably due to the image resolution and the level of energy dissipation for poly-fibers, while the XCT imaging was advantageous in evaluating the distribution and behavior of various fibers upon bending for fiber-reinforced concrete beam elements.
Seok Yong Lim and Tae Sup Yun — School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seoul 03722, Republic of Korea
Kwang Soo Youm — GS Construction & Engineering, 33 Jong-ro, Jongro-gu, Seoul 03159, Republic of Korea
Kwang Yeom Kim — Department of Energy & Resources Engineering, Korea Maritime & Ocean University, Taejong-ro, Youngdo-gu, Busan 49112, Republic of Korea
Yong-Hoon Byun — School of Agricultural Civil & Bio-Industrial Engineering, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea
Young K. Ju — School of Civil, Environmental and Architectural Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
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