Concrete Research and Technology
Online ISSN : 2186-2745
Print ISSN : 1340-4733
ISSN-L : 1340-4733
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Volume 18, Issue 3
Displaying 1-4 of 4 articles from this issue
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  • Influence of Compressive Stress on Chloride Penetration into Concrete mixed with Blast Furnace Slag or Fly Ash
    Yuki Sakoi, Masahiro Kawakita, Takashi Horiguchi
    2007 Volume 18 Issue 3 Pages 1-7
    Published: September 25, 2007
    Released on J-STAGE: November 13, 2012
    DOIhttps://doi.org/10.3151/crt1990.18.3_1
    JOURNAL FREE ACCESS
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    Many studies on chloride penetration into concrete were reported, however a few attempts have been done so far for the chloride penetration into stressed concrete. The purpose of this study is to clarify the influence of stress-strength ratio on chloride penetration into concrete mixed with blast furnace slag or fly ash. From the experimental results, it was found that the diffusion coefficient under loading was affected by stress-strength ratio, and it was clear that the diffusion coefficient of stressed concrete was different from that of non-loading or released condition. Moreover, it was observed that micro-crack in stressed concrete was different from that of released concrete, and it was considered that the difference of diffusion coefficient between stressed concrete and released concrete was due to the difference of this crack condition.
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  • An Experimental Study on Freeze-Thaw Resistance and Plant Growth of Porous Concrete Containing Silica Fume and Fine Fibers
    Teppei Otomo, Koji Otsuka, Masafumi Kitatsuji, Minoru Aba
    2007 Volume 18 Issue 3 Pages 9-22
    Published: September 25, 2007
    Released on J-STAGE: November 13, 2012
    DOIhttps://doi.org/10.3151/crt1990.18.3_9
    JOURNAL FREE ACCESS
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    Porous concrete is expected as an environmental preservation-type concrete but causes concern about its low freeze-thaw resistance compared with that of normal concrete. The purpose of this study is to clarify the effect of silica fume and fine fibers, a new material, on the freeze-thaw resistance of porous concrete. This study also included a vegetation experiment on porous concretes of the same kinds to observe the growth of plants. As a result, the freeze-thaw resistance of porous concrete was significantly improved when10-30% silica fume and 1Vol% fibers were used, with large differences in the state of deterioration and number of cracks being observed between normal porous concrete and fiber reinforced porous concrete containing silica fume. The growth of plants on fiber reinforced porous concrete was found to be comparable to that on normal porous concrete.
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  • Effect of Curing Condition and Carbonation on Hydration of Blast Furnace Slag Cement
    Takahiro Sagawa, Toyoharu Nawa
    2007 Volume 18 Issue 3 Pages 23-35
    Published: September 25, 2007
    Released on J-STAGE: November 13, 2012
    DOIhttps://doi.org/10.3151/crt1990.18.3_23
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    Ordinary Portland cement and blast furnace slag cement pastes with various water to binder ratio between 30 to 50% were hydrated under different curing conditions. Hydration ratio of cement compounds and slag, amount of hydration products were determined quantitatively by Rietveld method. Hydration of BFS is a little delayed in air-dried curing of 60%RH. CaO/SiO2 molar ratio of C-S-H decrease as increasing the amount of produced Ca (OH) 2; CaO/Si02 molar ratio of C-S-H in blast furnace slag cement is about 1.6, ordinary Portland cement is about 1.8 at the age of 91 days in water curing. CaO/Si02 molar ratio of C-S-H in blast furnace slag cement and ordinary Portland cement remarkably decrease below 1.0 from carbonation.
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  • Study on Heat Emission Power and Image Processing of Active Heating Thermography Method for Detection of Concrete Spalling
    Michiaki Oyado, Hisashi Tanaka, Seiichi Tottori, Koichi Kurita
    2007 Volume 18 Issue 3 Pages 37-46
    Published: September 25, 2007
    Released on J-STAGE: November 13, 2012
    DOIhttps://doi.org/10.3151/crt1990.18.3_37
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    To detect the spalling of the deteriorated concrete surface, active infrared thermography method using the Xenon-Arc Lamp heating system has already been developed. To simplify the heating device system and widen applicable condition, reduced heat emission power was applied to the inspection test on the existing reinforced concrete viaduct. According to the test result, spalling can be detected with the reduced heat emission power, but distinction between the part without deterioration and the spalled part came to be rather ambiguous. To solve the latter problem, a new infrared image processing method focused on the changing trend of the temperature distribution was developed and its availability was proved.
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