【公開日：2023.08.01】【最終更新日：2024.07.01】

課題データ / Project Data

課題番号 / Project Issue Number

22QS0016

利用課題名 / Title

Investigation of the structural changes and deformation behavior of N-A-S-H under compressive load and high temperature

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）マテリアルの高度循環のための技術/Advanced materials recycling technologies（副 / Sub）その他/Others

キーワード / Keywords

Environmentally friendly material design, Nano-structural analysis,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

Department of Architectural Engineering, Hanyang University

共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes

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

QS-222：高速2体分布関数計測装置

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

Sodium aluminosilicate hydrate (N-A-S-H) is the main hydration product of geopolymers with sodium activators. The usage of geopolymers in construction varies with their Si/Al ratio, as the mechanical and chemical properties of geopolymer changes. In this work, we synthesized metakaolin-based geopolymer pastes with different Si/Al ratios by using pure metakaolin, silica fume, and sodium activators (NaOH and Na₂SiO₃). The mechanical properties of the pastes were evaluated by subjecting external axial loading during X-ray scattering experiments. Furthermore, the mechanical properties of metakaolin-based geopolymers exposed to high temperatures were assessed as well to test the stability of the N-A-S-H structure under high temperatures.

実験 / Experimental

【利用した装置】：高速2体分布関数計測装置
【実験方法】
The metakaolin-based geopolymer (N-A-S-H) pastes were synthesized with different Si/Al ratios. Si/Al = 2.0, 2.25, 2.5, 2.75, and 3.0 were selected for the synthesis as N-A-S-H structures are known to be stable around ratio with Si/Al = 2.5. The sodium activators were prepared by mixing water, NaOH, and Na₂SiO₃. The activator was later mixed with metakaolin (kaolinite calcinated under 800°C for 3 h) and silica fume. To test the stability of the N-A-S-H pastes under high temperatures, the pastes were pre-heated at 400, 800, and 1200℃ at a heating rate of 10 ℃/min. The synthetic pastes were 5×5×10 mm³ and stored in vacuum packed bags to minimize carbonation before experiments. The distance from the specimen on the compression stage to IP was set to 375 mm and 725 mm to gain a long Q-range for the PDF and high angular resolution for the Bragg peak.
Since N-A-S-H gel mostly comprises the geopolymer pastes, which has an amorphous aluminosilicate structure, in-situ high-energy X-ray total scattering experiments (69.8 keV, λ = 0.178 Å, BL22XU beamline in SPring-8, Hyogo, Japan) were performed to observe the local atomic structure of geopolymer with different Si/Al ratios and the nano-structural deformation caused by the compressive load applied during the experiments (20 N/step), and two strain gauges were attached to the sample on each side to measure the macroscopic strain as well.

結果と考察 / Results and Discussion

Due to the amorphous structure of N-A-S-H structure, all geopolymer samples showed short coherence length of 5 Å. With increasing Si/Al ratio, the atomic distance of T-O (Si,Al-O) decreased as Si-O is shorter than Al-O. The distances of Na-O and T-T also decreased with increasing Si/Al ratio, which means a denser matrix are formed at higher Si/Al ratio (Fig. 1). The atomic number density (ρ₀) from the tangent slope -4πρ₀*r value, at r (the distance of first local minimum value in the range between rmin (2π/Q_max) and the 1st coordination peak) also supported this conclusion. However, the atomic-scale elastic modulus (E) calculated with in-situ X-ray scattering experiment data (Fig. 2) showed that while the E decreased with increasing Si/Al ratio until 2.5, there was a sudden increase at Si/Al = 2.75, which was expected to be the effect of unreacted silica fume due to lack of Al  (Fig. 3). Moreover, The minimized gap between the two directions in the N-A-S-H structure of MG250 could indicate the most well-connected 3D aluminosilicate network in the Si/Al ratio of 2.5.
In addition, the N-A-S-H paste with Si/Al = 2.5 showed the highest compressive strength, and there was a decrease of compressive strength in Si/Al =2.75 and 3.0, which was induced by the unreacted silica fume which failed to be incorporated into N-A-S-H structure.

図・表・数式 / Figures, Tables and Equations

Fig. 1. PDF of metakaolin-based geopolymer with different Si/Al ratios in the range of 0–6 Å

Fig. 2. The linear fitting of compressive strength and interatomic strain of (a) MG225(Si/Al = 2.25) and (b) MG250 (Si/Al = 2.5), and linear fitting of compressive strength and strain of d-spacing of (c) MG225 and (d) MG250

Fig. 3. Average atomic-scale elastic modulus of metakaolin-based geopolymer at axial and lateral direction obtained from (a) PDF and (b) XRD results. Also, (c) macroscopic elastic modulus and (d) stress and strain curve until 16 MPa are shown for comparison.

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

・参考文献
R.Z. Si, S.C. Guo, Q.L. Dai, J.Q. Wang, Atomic-structure, microstructure and mechanical properties of glass powder modified metakaolin-based geopolymer, Constr Build Mater, 254 (2020) 119303.
J.L. Bell, P. Sarin, P.E. Driemeyer, R.P. Haggerty, P.J. Chupas, W.M. Kriven, X-ray pair distribution function analysis of a metakaolin-based, KAlSi₂O₆▪5.5H₂O inorganic polymer (geopolymer), J. Mater. Chem., 18 (2008) 5974-5981.
C.E. White, K. Page, N.J. Henson, J.L. Provis, In situ synchrotron X-ray pair distribution function analysis of the early stages of gel formation in metakaolin-based geopolymers, Appl Clay Sci, 73 (2013) 17-25.

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)

1. Gyeongryul Kim, Effect of magnesium silicate hydrate (M-S-H) formation on the local atomic arrangements and mechanical properties of calcium silicate hydrate (C-S-H): In situ X-ray scattering study, Cement and Concrete Research, 159, 106869(2022).
   DOI: 10.1016/j.cemconres.2022.106869
   
2. Gyeongryul Kim, Impact of interatomic structural characteristics of aluminosilicate hydrate on the mechanical properties of metakaolin-based geopolymer, Construction and Building Materials, 411, 134529(2024).
   DOI: 10.1016/j.conbuildmat.2023.134529
   

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

1. Gyeongryul Kim, Heongwon Suh, Sungchul Bae, “Investigation of the physicochemical characteristics of metakaolin-based” 2022 Fall Conference for Korea Institute for Structural Maintenance and Inspection, 令和4年10月07日.
2. Sumin Im, Seongmin Cho, Sungchul Bae, “A Study on the High-Temperature Characteristics of Synthetic Calcium Silicate Hydrate (C-S-H) According to Ca/Si Ratios” 2022 Fall Conference for Korea Concrete Institute, 令和4年11月03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