Acceleration of calcium leaching in concrete and evaluation of the influence on mechanical properties

• Project/Area Number: 16K06446
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Civil engineering materials/Construction/Construction management
• Research Institution: Hokkaido University of Science
• Principal Investigator: Katsuyuki Konno 北海道科学大学, 工学部, 教授 (80290667)
• Research Collaborator: Schwotzer Matthias
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000); Fiscal Year 2018: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2017: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2016: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
• Keywords: 凍結防止剤 / カルシウム溶脱 / EPMA / 断面分割法 / ヤング係数 / 曲げ強度 / 塩がマグネシウム / 構造工学 / 土木材料

Outline of Final Research Achievements

In order to investigate the effect of various deicing agents to promote calcium leaching, the immersion test was carried out. It was shown that the degree of calcium leaching was different depending on the deterioration of the hardened cement paste surface. Based on this result, the bending test of hardened cement paste which caused calcium leaching was conducted. After that, chemical analysis of hardened cement paste was carried out to investigate the calcium concentration on the cross section. Then, using a statistical method, the calcium concentration distribution was modeled. Furthermore, the modeling results were used for numerical analysis, and the influence of the decomposition of calcium hydroxide and calcium silicate hydrate, which are the main compounds of the hardened cement paste, on the mechanical properties was discussed.

Academic Significance and Societal Importance of the Research Achievements

ヨーロッパでは，放射性廃棄物の地層処分として岩塩坑が使われることがあり，各種の塩がカルシウム溶脱を促進する作用について様々な研究が行われている．一方，日本において，構造物が各種の塩の水溶液に曝されるのは寒冷地に限定される．すなわち，凍結防止剤が溶けた水に曝される道路構造物である．それらの劣化は凍害として扱われることが多く，カルシウム溶脱の影響はさほど重視されていないと思われる．本研究の成果は，寒冷地の道路構造物の補修計画に対して，カルシウム溶脱の影響を考慮する一助になったと考える．

Research Products

• [Int'l Joint Research] カールスルーエ工科大学(ドイツ)
• [Journal Article] The rim zone of cement-based materials - Barrier or fast lane for chemical degradation? (2016)
  • Author(s): Matthias Schwotzer, Katsuyuki Konno, Jonas Kaltenbach and Andreas Gerdes
  • Journal Title: Cement and Concrete Composites Volume: 74 Pages: 236-243
  • DOI: 10.1016/j.cemconcomp.2016.10.009
  • Peer Reviewed
• [Presentation] 溶脱よって生じた硬化セメントペーストのカルシウム濃度勾配のモデル化 (2019)
  • Author(s): 尾形優弥，森喜敬，Daniel Froehlich，今野克幸
  • Organizer: 土木学会北海道支部平成30年度年次技術研究発表会
• [Presentation] Impact of thermal loads on the chemical stability of cement-based materials (2016)
  • Author(s): Matthias Schwotzer, Olivia Wenzel, Jonas Kaltenbach, Katsuyuki Konno and Andreas Gerdes
  • Organizer: 2nd International Conference on the Chemistry of Construction Materials
  • Place of Presentation: ドイツ，ミュンヘン
  • Year and Date: 2016-10-10
  • Int'l Joint Research