【公開日：2025.06.10】【最終更新日：2025.04.17】
課題データ / Project Data
課題番号 / Project Issue Number
24QS0021
利用課題名 / Title
Nanoscale deformation behavior of cementitious calcium silicate hydrate upon chloride-sulfate attacks under different pH conditions
利用した実施機関 / Support Institute
量子科学技術研究開発機構 / QST
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）マルチマテリアル化技術・次世代高分子マテリアル/Multi-material technologies / Next-generation high-molecular materials（副 / Sub）-
キーワード / Keywords
セメント材料, 局所構造,X線回折/ X-ray diffraction,放射光/ Synchrotron radiation
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Bae Sungchul
所属名 / Affiliation
School of Architectural Engineering, College of Engineering, Hanyang University
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
冨永 亜希,Im Sumin,Cho Seongmin,Yun Jin,Kim Junho,Park Jin
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
町田 晃彦
利用形態 / Support Type
（主 / Main）共同研究/Joint Research（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
This study investigates the structural evolution and mechanical adaptations of calcium silicate hydrate (C–S–H) using pair distribution function (PDF) analysis under varying alkaline conditions. The primary aim is to elucidate how environmental pH influences structural coherence at both short-range (atomic-level) and long-range (globular scale) correlations, affecting mechanical stability. The PDF method uniquely captures local and intermediate structural changes crucial for understanding durability under high-pH conditions, applicable to fields such as nuclear waste storage, marine infrastructure, and subsurface cementitious systems. PDF analyses indicate significant local atomic rearrangements, structural densification at highly alkaline pH (13.5), and distinctive reorganization behaviors at intermediate alkaline pH (11). Results underscore the intricate relationship between chemical dissolution, reprecipitation mechanisms, and the hierarchical structural integrity of C–S–H.
実験 / Experimental
C–S–H pastes with Ca/Si ratios of 0.8 and 1.0 were synthesized using calcium hydroxide, silica gel, distilled water, and polycarboxylate superplasticizer, maintaining a water-to-solid ratio of 1.1. Post-synthesis, pastes were cured under controlled humidity conditions and sealed to prevent carbonation. Samples were subjected to dissolution in alkaline solutions at pH 7, 11, and 13.5 for 90 days. Post-dissolution, solids were vacuum-dried and analyzed using total X-ray scattering at the BL22XU beamline of SPring-8 synchrotron facility. PDF analyses were conducted from total scattering data, capturing atomic-scale structural details crucial for understanding dissolution-induced modifications.
PDF data were collected through synchrotron-based total X-ray scattering performed at the BL22XU beamline of the SPring-8 synchrotron facility. Cuboid C–S–H pastes (5 × 5 × 10 mm³) prepared with Ca/Si ratios of 0.8 and 1.0 were equilibrated in solutions at different pH levels (7, 11, and 13.5) for 90 days. In-situ uniaxial loading experiments were conducted during PDF measurements, providing direct insights into structural changes under mechanical stress. The scattering intensity was processed into PDF spectra using PDFgetX3 software.
結果と考察 / Results and Discussion
The PDF spectra revealed crucial insights into the atomic and intermediate structural evolution of C–S–H under varying alkaline conditions. Short-range features (1–8 Å) indicated enhanced atomic reorganization, particularly pronounced at pH 13.5, characterized by significant increases in structural coherence and densification. Peaks associated with Si–O and Ca–O bonds confirmed extensive silicate depolymerization and subsequent reorganization at high pH, corroborated by reductions in Si–O peak intensity.Intermediate-range analysis (20–40 Å) displayed structural coherence disparities, with the highest coherence observed at pH 13.5 due to densification via dissolution-reprecipitation mechanisms. Contrarily, at pH 11, lower structural coherence suggested smaller, highly reorganized globular domains, indicative of selective reprecipitation and hierarchical restructuring. This demonstrates that structural rearrangement can optimize mechanical performance by balancing localized flexibility and enhanced long-range rigidity, particularly prominent at pH 11. These structural adaptations underscore the role of dissolution-driven densification and sodium incorporation influencing C–S–H durability and mechanical behavior under alkaline environments.
図・表・数式 / Figures, Tables and Equations
Fig. 2. PDF spectra of the solid phase as functions of initial solution pH for (a) Ca/Si = 0.8 in the 1–8 Å range, (b) Ca/Si = 0.8 in the 20–40 Å range, (c) Ca/Si = 1.0 in the 1–8 Å range, and (d) Ca/Si = 1.0 in the 20–40 Å range.
Fig. 1. PDF spectra of the solid phase, illustrating the effect of initial solution pH and Ca/Si ratios across a range of 1–50 Å.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
The findings extend the understanding of dissolution-reprecipitation behavior at atomic and intermediate scales, significantly contributing to the broader research on cementitious durability in chemically aggressive environments. Future work should further explore the mechanical implications of these structural transformations.The authors gratefully acknowledge the support from SPring-8 for synchrotron facilities and technical assistance from the staff at BL22XU beamline. This work builds upon methodologies and frameworks established in prior studies.
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
- Yun Jin, Bae Sungchul, "Impact of Chloride and Sulfate Exposure on the Physicochemical Properties of Calcium Silicate Hydrate (C-S-H) at Various pH Levels", 51st Cement Symposium (Pyeongchang/Republic of Korea), 令和6年7月19日.
- Park Jin, Bae Sungchul, "Investigation on the Properties of Early Hydration Products in Thermally Activated and Rehydrated C3S Paste", Korea Concrete Institute 2024 Fall Conference (Gangwon State/Republic of Korea), 令和6年11月8日.
- Yun Jin, Bae Sungchul, "Stability and Mechanical Behavior of Calcium Silicate Hydrate (C-S-H) under Alkaline pH Conditions", Korea Concrete Institute 2024 Fall Conference (Gangwon State/Republic of Korea), 令和6年11月8日.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件