EFFECT OF CHANGE OF Al BONDING STATE BY THERMAL DEHYDRATION AND REWETTING ON CHARACTERISTIC OF WATER ADSORPTION-CONSIDERING THE EFFECT OF Al BONDING STATE ON SECONDARY ETTRINGITE FORMATION NO.1-

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  • NOZAWA Risako
    NIIGATA UNIVERSITY, Graduate School of Science and Technology（8050, Ikarashi-2, Nishi-ku, Niigata-shi, Niigata 950-2181, Japan）
  • SAITO Tsuyoshi
    NIIGATA UNIVERSITY, Department of Civil Engineering（8050, Ikarashi-2, Nishi-ku, Niigata-shi, Niigata 950-2181, Japan）
  • SATO Kennosuke
    YAMANASHI UNIVERSITY, Department of Civil Engineering（4-3-11, Takeda, Kofu-shi, Yamanashi 400-8511, Japan）
  • SAEKI Tatsuhiko
    NIIGATA UNIVERSITY, Department of Civil Engineering（8050, Ikarashi-2, Nishi-ku, Niigata-shi, Niigata 950-2181, Japan）

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  • エトリンガイトの加熱脱水・再吸水によるAl結合状態の変化が水分吸着性状に及ぼす影響─Alの結合状態がエトリンガイトの二次生成に及ぼす影響の検討　その1─

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<p>Sulfate attack is known as one of the deterioration phenomena of concrete structures. In particular, there is a serious problem with expansion due to Delayed Ettringite Formation（DEF）. Recent researches had indicated the possibility that CO32－ promotes DEF expansion. Therefore, we focused on understanding carbonate ettringite, in which ettringite substitutes SO42－ for CO32－, despite it has never detected in hardened cement. Our purpose is to discuss the relationship between the secondary formation of ettringite and Al bonding state, by comparing ettringite and carbonate ettringite.<br/>From the experimental results, thermal dehydration converted carbonate ettringite into amorphous carbonate ettringite, as shown by XRD, while Al coordination of dehydrated carbonate ettringite was 4 and 5. In addition, water adsorption isotherm of dehydrated carbonate ettringite showed a sharp rise at RH60-80％. It is possible that carbonate ettringite formed as a secondary carbonate ettringite when Al coordination number was 4 or 5, and up to 6, by water supply. Therefore, it is concluded that dehydrated carbonate ettringite has large potential of swelling compared to carbonate ettringite.</p>

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