Journal of Advanced Concrete Technology
Online ISSN : 1347-3913
ISSN-L : 1346-8014
  • Yuga Yano, Taito Shiokoshi, Yuya Takase, Yutaro Ishida, Takahide Abe, ...
    2024 年 22 巻 4 号 p. 178-189
    発行日: 2024/04/03
    公開日: 2024/04/03
    ジャーナル フリー

    Reinforced concrete (RC) structures in cold regions are susceptible to surface deterioration due to freeze-thaw cycles (FTC). For sustainable development goals (SDGs) and a decarbonized society, damaged structures should be repaired and reinforced. Post-installed anchors are commonly used for seismic retrofitting and equipment fixation. However, research on the bond characteristics of damaged concrete is limited. Therefore, in this study, the bonding performance of adhesive anchors in damaged concrete was investigated. Liquid nitrogen was employed to subject the concrete surface to FTC; subsequently, bond-slip tests were conducted with the degree of deterioration serving as a parameter. The results suggested, the bond strength decreased as the degree of damage increased. The reduction ratios of the post-installed anchor with epoxy and cement-based resins were almost identical. Furthermore, a bond strength equation was proposed by referring to the bond-slip model between the rebar and concrete (fib 1990). The test results were well predicted with a correlation coefficient of 0.94. This study is based on previous studies (Yano et al. 2022, 2023) but presents new findings.

  • Francesca Bonfante, Giuseppe Ferrara, Pedro Humbert, Davide Garufi, Je ...
    2024 年 22 巻 4 号 p. 207-218
    発行日: 2024/04/12
    公開日: 2024/04/12
    ジャーナル フリー

    Electric Arc Furnace slag (EAF slag) reuse is currently limited by its inconsistent chemical composition and volume instability. However, the alkaline composition suggests the possibility to use this material for carbon capture and storage. This study investigated the CO2 uptake of EAF slag using a direct aqueous carbonation technique. The process was implemented at room temperature and ambient pressure, with minimized energy consumption. The CO2-reactive phases were identified through X-ray diffraction analysis. Different CO2 quantification techniques were employed: thermogravimetric analysis, acid digestion and thermal decomposition. The replicability of experiments and quantification techniques was assessed through analysis of variance and pairwise comparisons. The average CO2 uptake and coefficient of variation resulted respectively 7.9% and 9.0%, with a carbonation degree of about 34%, proving that this simple mineralization process can be promising even in mild conditions.

  • Mitsuhiko Ozaki, Yasuhiko Sato, Eiji Yoshida, Aya Takeuchi, Yuta Yamad ...
    2024 年 22 巻 4 号 p. 190-206
    発行日: 2024/04/05
    公開日: 2024/04/05
    ジャーナル フリー

    In previous studies on the bond behaviors of FRP sheets attached to concrete, specimens for bond tests that contained FRP sheets with relatively low stiffnesses were used. However, in actual strengthening design, high stiffnesses of FRP sheets are required because the scale of the structure is very large. Therefore, in this study, bond tests were conducted using specimens with many different sheet stiffnesses and with polyurea resin. As a result, the bond strength increased as the stiffness increased with multiple CFRP sheets. Nevertheless, existing bond strength models overestimated the bond strength when the stiffness exceeded 200 kN/mm. In addition, 3D scanning measurements of patterned and indented concrete thin layers behind CFRP sheets revealed that the interfacial fracture energy was strongly related to the surface area of the concrete thin layer, not to the CFRP sheet stiffness or the resin properties.

    This paper is an English translation of the authors’ previous work [Ozaki, M., Sato, Y., Yoshida, E., Takeuchi, A., Yamada, Y. and Nagashima, F., (2023). “Assessment on bond strength of CFRP sheet bonded to concrete focused on sheet stiffness.” Journal of JSCE, 79(6), 22-00289. (in Japanese)].