A study on water tightness and chloride penetration of hydrophobic concrete

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K18130
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Civil engineering materials/Construction/Construction management
• Research Institution: Saitama University
• Principal Investigator: Luan Yao 埼玉大学, 理工学研究科, 助教 (20725288)
• Research Collaborator: ASAMOTO Shingo ; YONEDA Taiju
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: コンクリート / 水分浸透 / 撥水 / 塩化物イオン / 鉄筋腐食 / ひび割れ / 強度 / 収縮

Outline of Final Research Achievements

In this study, cement mortars that have bulk hydrophobicity were made, and their properties, for example, water absorption and chloride resistance, were studied experimentally. First, two types of hydrophobic mortars were made by directly adding a hydrophobic agent in mixing or spraying the agent on sand before mixing. Hydrophobicity was confirmed by measuring contact angle. Then, water absorption test was performed under uncracked and cracked conditions. It was found that, because of the bulk hydrophobicity, the surfaces of cracks were water repellent, leading to less water absorption for the hydrophobic mortars. After that, experiments of chloride penetration and corrosion were carried out. The results indicated that the hydrophobic mortars showed less chloride diffusion, resulting to a less corrosion for the rebars inside the mortars. Finally, strength and shrinkage behaviors were measured. The hydrophobic mortars were found to have a lower strength but less shrinkage.

Free Research Field

コンクリート材料

Academic Significance and Societal Importance of the Research Achievements

撥水性をコンクリートの表層に付与する表面含浸工法が多く使われているが，ひび割れが撥水層より深く進行した場合，ひび割れを通じてコンクリート内部に水分が浸透する可能性が指摘されている。本研究では，撥水材を混和材としてモルタルとコンクリートに混入し，表層のみならず内部にも撥水性を付与する。こういった内部撥水性により，ひび割れが発生してもコンクリートの水分浸透と塩化物イオン侵入に対する抵抗性が低下せず，長期耐久性の向上に期待が寄せられている。