The Alteration Test of Hydrate Cement Paste by Water-Permeation using Centrifugal Force

Haga, Kazuko; Shibata, Masahito; Fukaya, Yasubumi; Kobayashi, Yasutoshi; Imamura, Mitsutaka

doi:10.3327/jnuce.6.167

Cited by 6 publications

(3 citation statements)

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“…It is estimated that Ca(OH) 2 is dissolved out and dissolution of C-S-H gel takes place when Ca/Si ratio of whole sample becomes lower than 1.8, as mentioned in the Introduction. Because these dissolution behaviors are the same result of penetration experiment of Haga et al, 5) it was confirmed that the penetration experiment in this study was performed successfully.…”

Section: Methodssupporting

confidence: 73%

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Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Miyamoto

Uehara

Sasoh

et al. 2006

Journal of Nuclear Science and Technology

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Application tests for advanced TEM analysis techniques were carried out to study the cement alteration processes associated with water penetration at high spatial resolution. Prior to TEM analysis, we measured the changes in the penetration coefficient and determined the characteristics of the penetrating water in order to gain a fuller understanding of the overall process. These experiments revealed that the process begins with the preferential dissolution of Ca(OH) 2 . After most of the Ca(OH) 2 is dissolved out, the penetration coefficient increases, while the pH value of the water decreases. It has been demonstrated that scanning transmission electron microscope (STEM) techniques are quite useful for determining local structures and compositions in the cement at sub-micron meter spatial resolution. The preferential dissolution of Ca ions results in refinement of cement grains. When the Ca/Si ratio decreases to 1.05, most grains have a round shape in the sub-micron range. X-ray mapping suggests the formation of 3CaOÁAl 2 O 3 Á xSiO 2 Á(6À2x)H 2 O (x¼0{3). Ettringite has been mostly dissolved out. But Mg ions remain still in form of brucite. When Ca/Si reaches 0.91, the morphology has changed to a mixture of fibers and granules. The fibers have been identified as a mixture of Calcium Silicate Hydrate Gel and silica gel. Quantitative EDX composition analyses have demonstrated that the granules are altered products of hydrogrossular, 3CaOÁAl 2 O 3 Á2SiO 2 Á2H 2 O, which have been predicted by previous theoretical studies. It is also been shown that hydrotalcite with Mg and Al has been also formed. The results thus obtained are in principle in accordance with the process predicted by previously proposed thermodynamic models.

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Section: Methodssupporting

confidence: 73%

“…Corresponding to the above theoretical considerations, Haga et al 5) carried out a water penetration experiment on the ordinary portland cement. The Ca/Si ratio in cement was decreased by penetration experiment, and the mineral specification was measured by X-ray diffraction.…”

Section: Original Papermentioning

confidence: 99%

Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Miyamoto

Uehara

Sasoh

et al. 2006

Journal of Nuclear Science and Technology

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“…The PSD of 11 × 11 × 22 cm 3 DEF-Ini and DEF-Fin1 samples, are given in Fig.4(a). It can be concluded that after DEF, pores between 4 and 30nm are filled by ettringite (red zone in Fig.4(a)), and the pore volume increases between 100nm and 10µm (dark yellow zone in Fig.4(a)), which may be caused by the dissolution of portlandite [29,30,31,32] and the generation of microcracks [26,33].…”

Section: The Evolution Of Psd Before and After Defmentioning

confidence: 99%

Locating ettringite due to DEF at the pore scale of cement paste by heat-based dissolution tests

Metalssi

Martin

et al. 2020

Construction and Building Materials

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An innovative experimental method, based on the thermal stability of ettringite, is proposed and implemented to dissolve the crystalline products formed during Delayed Ettringite Formation (DEF). The tests are designed to empty all the pores that are filled by ettringite during their formation. By characterising the porous structure before and after the heat-based dissolution test (HBDT) via Mercury Intrusion Porosimetry (MIP), it is proved that the pores filled by ettringite during DEF in the pore size range between 4 and 30nm are emptied and that the pore size distribution (PSD) in this range is reversed, approaching the initial state (i.e. before the degradation induced by DEF). This observation helps to confirm the location of ettringite formed during DEF.

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Change in pore structure and composition of hardened cement paste during the process of dissolution

Haga

Shibata

Hironaga

et al. 2005

Cement and Concrete Research

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The Alteration Test of Hydrate Cement Paste by Water-Permeation using Centrifugal Force

Cited by 6 publications

References 0 publications

Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Locating ettringite due to DEF at the pore scale of cement paste by heat-based dissolution tests

Change in pore structure and composition of hardened cement paste during the process of dissolution

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