Journal of Advanced Concrete Technology
Online ISSN : 1347-3913
ISSN-L : 1346-8014
Volume 18, Issue 1
Displaying 1-3 of 3 articles from this issue
Scientific paper
  • Arslan Qayyum Khan, Pengru Deng, Takashi Matsumoto
    2020 Volume 18 Issue 1 Pages 1-16
    Published: January 16, 2020
    Released on J-STAGE: January 16, 2020

    This study proposes approximate boundary conditions for a panel reinforced concrete (RC) slab to simulate the fatigue behaviors of a real bridge RC slab. To validate the approach, fatigue analysis of the panel RC slab is conducted using a finite element method (FEM) based numerical model with the bridging stress degradation concept. Both the proposed approximate boundary conditions, and those that have been typically employed in past studies, are used. The numerical results demonstrate that the panel RC slab with approximate boundary conditions experiences the same bending moment distribution and deformations around the loading locations as the load moves along the slab axis, similar to those of a real bridge RC slab. Moreover, the approximate boundary conditions reproduce the extensive grid crack pattern in the panel RC slab, which is similar to that generally observed in a real bridge RC slab. The results of this study establish that panel RC slab with approximate boundary conditions behaves in a similar manner to a real bridge RC slab, which results in a more realistic fatigue life estimation.

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  • Guoju Ke, Jun Zhang
    2020 Volume 18 Issue 1 Pages 17-26
    Published: January 18, 2020
    Released on J-STAGE: January 18, 2020

    In this paper, the effects of retarding admixture, polycarboxylate (PCE) superplasticizer and supplementary cementitious material (SCM) on the rheology of high strength calcium sulfoaluminate (CSA) cement paste are investigated. At the water to binder ratio of 0.3, one PCE, two retarding admixtures, and three SCMs were used in the test. The test results show that much more PCE is needed for paste with citric acid than that with sodium borate to achieve a similar initial flowability. The reference paste and pastes mixed with sodium borate or fly ash exhibit shear thickening; pastes mixed with citric acid or silica fume exhibit shear thinning. The addition of citric acid increases the maximum shear stress of pastes, while the maximum shear stress can be significantly reduced by silica fume. Both the retarding admixtures and SCMs will strongly reduce the early-age compressive strength of the cement paste. At 28 days of age, CSA cement paste incorporating retarding admixtures has comparable strength to the reference paste. Silica fume has less negative effect on the compressive strength of the CSA cement paste due to the significant filling effect.

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  • Hiroshi Ueda, Yuya Sakai, Koji Kinomura, Kenzo Watanabe, Tetsuya Ishid ...
    2020 Volume 18 Issue 1 Pages 27-38
    Published: January 29, 2020
    Released on J-STAGE: January 29, 2020

    The current durability design for carbonation estimates that dry concrete experiences higher corrosion; however, in actual concrete structures, higher corrosion is observed in wet concrete. To solve this contradiction, a durability design method considering water penetration is proposed, in which the reinforcement is assumed to be corroded by contacting with water. The reinforcement corrosion depth is calculated as the accumulation of the stepwise corrosion. To calculate the number of annual contacts of water with the reinforcement, an equation to calculate the annual frequency of precipitation and a coefficient to take into account the effect of the water supply conditions are established. The comparison of the proposed method with an existing carbonation verification method indicates that the proposed method reflects the situation of an actual concrete structure more appropriately. The proposed durability design method was incorporated in the Standard Specifications for Concrete Structures of the Japan Society of Civil Engineers in 2017.

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