Details
| Original language | English |
|---|---|
| Article number | 104582 |
| Journal | Applied geochemistry |
| Volume | 118 |
| Early online date | 22 May 2020 |
| Publication status | Published - Jul 2020 |
Abstract
Celitement is a new type of cement that is based on hydraulic calcium-hydrosilicate (hCHS). It is produced by mechanochemical activation of Calcium-Silicate-Hydrates (C-S-H) in a grinding process. Due to the lack of typical clinker minerals, its CaO/SiO 2 (C/S) ratio can be minimized from above 3 (as in Ordinary Portland Cement) down to 1, which significantly reduces the amount of CO 2 released during processing. The reaction kinetics of hCHS differs from that of classical clinker phases due to the presence of highly reactive silicate species, which involve silanol groups instead of pure calcium silicates and aluminates and aluminoferrites. In contrast to Portland cement, no calcium hydroxide is formed during hydration, which otherwise regulates the Ca concentration. Without the buffering role of Ca(OH) 2 the concentration of the dissolved species c(Ca 2+) and c(SiO 4 4−) and the corresponding pH must be controlled to ensure a reproducible reaction. Pure hCHS reacts isochemically with water, resulting in a C-S-H phase with the same chemical composition as a single hydration product, with a homogeneous distribution of the main elements Ca and Si throughout the sample. Here we study via nanoindentation tests, the mechanical properties of two different types of hardened pastes made out of Celitement (C/S = 1.28), with varying amounts of hCHS and variable water to cement ratio. We couple nanoindentation grids with Raman mappings to link the nanoscale mechanical properties to individual microstructural components, yielding in-depth insight into the mechanics of the mineralogical phases constituting the hardened cement paste. We show that we can identify in hardened Celitement paste both fresh C-S-H with varying density, and C-S-H from the raw material using their specific Raman spectra, while simultaneously measuring their mechanical properties. Albeit not suitable for phase identification, supplemental EDX measurements provide valuable information about the distribution of alkalis, thus further helping to understand the reaction pattern of hCHS.
Keywords
- Hydraulic calcium –hydrosilicate, Nanoindentation, Raman spectroscopy
ASJC Scopus subject areas
- Environmental Science(all)
- Pollution
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
- Environmental Science(all)
- Environmental Chemistry
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In: Applied geochemistry, Vol. 118, 104582, 07.2020.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Chemo-mechanical characterization of hydrated calcium-hydrosilicates with coupled Raman- and nanoindentation measurements
AU - Stemmermann, P.
AU - Garbev, K.
AU - Gasharova, B.
AU - Beuchle, G.
AU - Haist, M.
AU - Divoux, T.
PY - 2020/7
Y1 - 2020/7
N2 - Celitement is a new type of cement that is based on hydraulic calcium-hydrosilicate (hCHS). It is produced by mechanochemical activation of Calcium-Silicate-Hydrates (C-S-H) in a grinding process. Due to the lack of typical clinker minerals, its CaO/SiO 2 (C/S) ratio can be minimized from above 3 (as in Ordinary Portland Cement) down to 1, which significantly reduces the amount of CO 2 released during processing. The reaction kinetics of hCHS differs from that of classical clinker phases due to the presence of highly reactive silicate species, which involve silanol groups instead of pure calcium silicates and aluminates and aluminoferrites. In contrast to Portland cement, no calcium hydroxide is formed during hydration, which otherwise regulates the Ca concentration. Without the buffering role of Ca(OH) 2 the concentration of the dissolved species c(Ca 2+) and c(SiO 4 4−) and the corresponding pH must be controlled to ensure a reproducible reaction. Pure hCHS reacts isochemically with water, resulting in a C-S-H phase with the same chemical composition as a single hydration product, with a homogeneous distribution of the main elements Ca and Si throughout the sample. Here we study via nanoindentation tests, the mechanical properties of two different types of hardened pastes made out of Celitement (C/S = 1.28), with varying amounts of hCHS and variable water to cement ratio. We couple nanoindentation grids with Raman mappings to link the nanoscale mechanical properties to individual microstructural components, yielding in-depth insight into the mechanics of the mineralogical phases constituting the hardened cement paste. We show that we can identify in hardened Celitement paste both fresh C-S-H with varying density, and C-S-H from the raw material using their specific Raman spectra, while simultaneously measuring their mechanical properties. Albeit not suitable for phase identification, supplemental EDX measurements provide valuable information about the distribution of alkalis, thus further helping to understand the reaction pattern of hCHS.
AB - Celitement is a new type of cement that is based on hydraulic calcium-hydrosilicate (hCHS). It is produced by mechanochemical activation of Calcium-Silicate-Hydrates (C-S-H) in a grinding process. Due to the lack of typical clinker minerals, its CaO/SiO 2 (C/S) ratio can be minimized from above 3 (as in Ordinary Portland Cement) down to 1, which significantly reduces the amount of CO 2 released during processing. The reaction kinetics of hCHS differs from that of classical clinker phases due to the presence of highly reactive silicate species, which involve silanol groups instead of pure calcium silicates and aluminates and aluminoferrites. In contrast to Portland cement, no calcium hydroxide is formed during hydration, which otherwise regulates the Ca concentration. Without the buffering role of Ca(OH) 2 the concentration of the dissolved species c(Ca 2+) and c(SiO 4 4−) and the corresponding pH must be controlled to ensure a reproducible reaction. Pure hCHS reacts isochemically with water, resulting in a C-S-H phase with the same chemical composition as a single hydration product, with a homogeneous distribution of the main elements Ca and Si throughout the sample. Here we study via nanoindentation tests, the mechanical properties of two different types of hardened pastes made out of Celitement (C/S = 1.28), with varying amounts of hCHS and variable water to cement ratio. We couple nanoindentation grids with Raman mappings to link the nanoscale mechanical properties to individual microstructural components, yielding in-depth insight into the mechanics of the mineralogical phases constituting the hardened cement paste. We show that we can identify in hardened Celitement paste both fresh C-S-H with varying density, and C-S-H from the raw material using their specific Raman spectra, while simultaneously measuring their mechanical properties. Albeit not suitable for phase identification, supplemental EDX measurements provide valuable information about the distribution of alkalis, thus further helping to understand the reaction pattern of hCHS.
KW - Hydraulic calcium –hydrosilicate
KW - Nanoindentation
KW - Raman spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=85085271660&partnerID=8YFLogxK
U2 - 10.1016/j.apgeochem.2020.104582
DO - 10.1016/j.apgeochem.2020.104582
M3 - Article
VL - 118
JO - Applied geochemistry
JF - Applied geochemistry
SN - 0883-2927
M1 - 104582
ER -