Seawater tolerance of cement stabilized soil due to magnesium hydroxide and its application for ground improvement techniques

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K18150
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geotechnical engineering
• Research Institution: Yamaguchi University (2017-2018); University of Miyazaki (2016)
• Principal Investigator: Hara Hiroyuki 山口大学, 大学院創成科学研究科, 講師 (00588709)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 土質安定処理 / セメント / 海水 / 劣化 / 水酸化マグネシウム

Outline of Final Research Achievements

In this study, it was investigated that white color sediments composed mainly of magnesium hydroxide generated at surface of cement stabilized soil under marine environment, and the following results were obtained. 1) White sediments prevent leaching of calcium from cement stabilized soil by inhibiting the infiltration of magnesium salts. 2) White sediments were generated when stabilized soil had high pH irrespective of stabilizer types. 3) An alkaline material was added at the time of preparation of cement stabilized soil to increase the pH in the soil. It was confirmed that the formation of sediments was promoted by adding the alkaline material, and deterioration suppression effect was given to cement treated soil.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

固化処理工法は，軟弱地盤対策として広く活用されているが，海水に含まれるMg塩が処理土のCa成分の溶出を促進する効果を持つため，沿岸域における耐久性が懸念されている．本研究では，海水と固化処理土の界面に生じる場合がある白色の析出物について詳細に調べた．その結果，析出物は劣化の原因物質であるMgを主体とする化合物であり，高い劣化抑制効果を持つことを示し，固化材の種類によらない生成条件を明らかにした．さらに，アルカリ助剤を添加することで析出物の生成を促進させる手法を開発した．得られた成果は，劣化対策技術の開発や耐海水性を付与する新たな固化材の開発に資するものであり，学術的にも大きな価値がある．