【公開日：2023.07.31】【最終更新日：2023.05.23】
課題データ / Project Data
課題番号 / Project Issue Number
22UT0021
利用課題名 / Title
RH effect on the nano-structure of synthesized C-A-S-H gel
利用した実施機関 / Support Institute
東京大学
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
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）その他/Others（副 / Sub）-
キーワード / Keywords
concrete, gel,電子顕微鏡/Electron microscopy
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)
yuqian zheng
所属名 / Affiliation
東京大学
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
Wang Tiao
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
Ayumi Kimura
利用形態 / Support Type
（主 / Main）技術補助/Technical Assistance（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 experiment is to characterize the C-A-S-H gel by Cryo-EM. And the effects of chemical compositions and RH on morphology of C-A-S-H gel are studied. Based on th experimental results, it can be observed from Cryo-EM images that the average length of interlayer spacing decreases as RH decreases, which represents the shrinkage of C-(A)-S-H gel during drying.
実験 / Experimental
1. Synthesis of C-(A)-S-H gel We used calcium nitrate (Ca(NO3)2∙4H2O), sodium silicate (Na2SiO3∙5H2O), and aluminum nitrate (Al(NO3)3∙9H2O) to synthsize various C-(A)-S-H gels by precipitation in an alkaline solution. The synthesized C-(A)-S-H gel is an alternative to the C-(A)-S-H gel in the cement system considering the complexity of hydration products of cement systems. In this study, five different C-(A)-S-H gel were synthesized for different chemical compositions. The chemical composition of different C-(A)-S-H gels was controlled by the initial Ca/Si and Al/Si ratios in the solution, and the chemical composition of the synthesized C-(A)-S-H gel is shown in Table 1.2. Sample preparationAfter synthesis, the C-(A)-S-H gel was first washed with deionized water to remove the precipitated Ca(OH)2. The washed samples were dispersed in deionized water by ultrasonic dispersion for 30 s. Three milliliter of the upper solution with C-(A)-S-H gel was dropped on a Cu microgrid (200 mesh, JEOL) with hydrophilic coating (IB-3, Eiko). To minimize the influence of ice during observation, the Cu microgrid with C-(A)-S-H gel was dried on vacuum for 7 days and re-saturated in a sealed plastic box at various relative humidity, which was maintained by saturated salt solution as potassium nitrate (KNO3) for RH 95%, potassium iodate (KI) for RH70% and potassium carbonate (K2CO3) for RH45%. The box was filled with N2 gas to prevent the carbonation. After one month, microgrids were plunge-frozen in liquid ethane.3. Cryo-EM observation After frozen, the microgrid with C-(A)-S-H gel was subsequently installed on a cryogenic transfer holder (914, Gatan) filled with liquid nitrogen and observed by a TEM system (JEM-2100F, JEOL) at 200 kV.
結果と考察 / Results and Discussion
1. Morphology of C-(A)-S-H gelThe morphology of C-S-H gels with various Ca/Si are shown in Figure 1 to Figure 3. From Figures, it is seen that the C-S-H gel with a Ca/Si ratio of 1.4 grows like spherical particles (Figure 1). It indicated that the C-S-H gel looks like a homogenous silicate glass and the interlay space was not easily observed. However, with high Ca/Si ratio, C-S-H gel looks more like a fibrous crystal (Figure 2 and Figure 3). The C-S-H gel sheets locally were agglomerated and the interlayer spacing was observed.The morphology of C-A-S-H gels with various Al/Si are shown in Figure 4 and Figure 5. They show that as the Al/Si ratio increases, the C-A-S-H gel become more condensed.2. Shrinkage of C-(A)-S-H gel Cryo-EM images for C-S-H gel under various RHs are shown in Figure 6, 7 and 8. From the Cryo-EM images, the C-(A)-S-H gel sheet at high RH is easily observed, but the C-(A)-S-H gel sheet at low RH is not evident on the same scale. Moreover, the interlayer spacing was calculated from these images by Fourier transform and shown in Figure 9. It found that the average length of interlayer spacing decreases as RH decreases, which represents the shrinkage of C-(A)-S-H gel during drying.
図・表・数式 / Figures, Tables and Equations
Table 1 Chemical compositions of C-(A)-S-H gel
Figure 1 Cryo-EM images of C-(A)-S-H gel with a Ca/Si ratio of 1.0
Figure 2 Cryo-EM images of C-(A)-S-H gel with a Ca/Si ratio of 1.4
Figure 3 Cryo-EM images of C-(A)-S-H gel with a Ca/Si ratio of 1.7
Figure 4 Cryo-EM images of C-A-S-H gel with a Al/Si ratio of 0.1
Figure 5 Cryo-EM images of C-A-S-H gel with a Al/Si ratio of 0.2
Figure 6 Cryo-EM images of C-A-S-H gel under RH 0%
Figure 7 Cryo-EM images of C-A-S-H gel under RH 45%
Figure 8 Cryo-EM images of C-A-S-H gel under RH 95%
Figure 9 Average interlayer spacing of C-(A)-S-H gel at various RH
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
This measurement was done with the help of Mrs. Kimura in Advanced Research Infrastructure for Materials and Nanotechnology at The University of Tokyo.
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.
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