Journal of Advanced Concrete Technology
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Volume 12 , Issue 1
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Scientific paper
  • Laurent Charpin, Alain Ehrlacher
    Volume 12 (2014) Issue 1 Pages 1-6
    Released: January 15, 2014
    JOURNALS FREE ACCESS
    In this work, we focus on estimating the proportion of gel created by Alkali-Silica Reaction (ASR) in concrete that can enter the Interface Transition Zone (ITZ) surrounding an aggregate at a given pressure. We consider the gel as a non-Newtonian fluid following a Darcy law with a threshold pressure gradient while invading a porous medium. We show that at equilibrium, the mass of gel that penetrates in the ITZ can be considered as proportional to the pressure surrounding the aggregates while the ITZ is not full yet, and then constant once the ITZ is full. This is fairly consistent with the common use of a "connected porosity" in the models dealing with mechanical features of ASR to estimate the volume of gel lost in the porosity. We also study briefly the kinetics of this process and the influence of the gel compressibility.
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  • Shunsuke Banba, Tetsuo Abe, Kazuma Nagaoka, Yuki Murakami
    Volume 12 (2014) Issue 1 Pages 7-23
    Released: January 29, 2014
    JOURNALS FREE ACCESS
    In this study, the bond behavior of corroded reinforced concrete (RC) was investigated by conducting pull-out tests on RC specimens with different corrosion crack widths. The confinement stress of concrete was evaluated by an expansion simulation using a non-explosive demolition agent, from which a confinement stress equation for RC with corrosion cracking was proposed. Bond strength linearly decreased with decreasing confinement stress in the concrete. The rate of decrease was independent of longitudinal corrosion crack width at the concrete surface, cover thickness, and reinforcement diameter. Furthermore, from the relationship between bond strength and confinement stress in concrete, equations for predicting bond stress and slip curve were proposed. Overall, the predicted values agreed well with the experimental results of other studies.
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  • Shigemitsu Hatanaka, Naoki Mishima, Akihiro Maegawa, Eisuke Sakamoto
    Volume 12 (2014) Issue 1 Pages 24-33
    Released: January 31, 2014
    JOURNALS FREE ACCESS
    In the present research, the influence of aggregate size on various characteristics (strength, permeability, water retention and water wicking) of small particle size porous concrete was examined. The properties of small particle size porous concrete using small size crushed stone (particle size: 0.6-1.2, 1.2-2.5 mm) were compared with those of ordinary porous concrete using ordinary size crushed stone (5-13 mm). According to the test results, compressive strength of porous concrete was not influenced to a significant degree by aggregate size, while flexural strength became higher with decreasing particle size. Also, it was shown that small particle size porous concrete is superior in water retention and wicking compared to ordinary particle size porous concrete. It should be noted, however, that permeability of small particle size porous concrete was rather low. Further, clarifying the configuration of voids in the porous concrete is essential for the quantitative discussion on the behaviors of water in porous concrete
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