Details
Original language | English |
---|---|
Article number | 9 |
Journal | Gels |
Volume | 8 |
Issue number | 1 |
Early online date | 23 Dec 2021 |
Publication status | Published - Jan 2022 |
Abstract
Lime-sand bricks of different ages were investigated using IR-spectroscopy, thermogravimetry, and X-ray diffraction/scattering. After subtraction of the dominant quartz contribution (80%), the IR spectra show the absorption peaks of the hydrothermally formed binder phases. The spectra also show the alteration of the binder during ageing under atmospheric conditions by the influence of CO2 forming carbonate and a condensed SiO2-gel (secondary gel). The alteration could also be proven in X-ray pattern, obtaining a separation between crystalline CSH and amorphous contributions in the freshly produced lime-sand brick, too. Here, the formation of CSHamorph could be understood as a precursor state (primary gel) to the crystallization of CSH phases. X-ray patterns of aged bodies of alkali-silicate solution activated slags (AAS), CEM-I/CEM-III pastes, and CEM-I concrete indicate that in all cases a similar amorphous CSH-type phase (CSHamorph) was formed, which is responsible for the hardening properties as the glue. The main X-ray peak of CSHamorph obtained using CuKα-radiation with a usual diffractometer is observed between 24◦ and 35◦ 2 Theta with maximum at about 29◦ 2 Theta, whereas it appears much more broadly distributed between 15◦ and 35◦ 2 Theta with maximum between 26◦ and 28◦ 2 Theta for a geopolymer body prepared using the reaction of alkali-silicate solution and metakaolin (AAMK). This is due to the network formed by siloxo and sialate units in the case of AAMK, given that any crystallization can be ruled out. The origin of increasing mechanical strength during the ageing of AAS mortars must be due to further crosslinking of the preformed siloxo chains. Thermal treatment up to 800◦C leads to a complete loss of any mechanical strength of the CEM pastes due to the destruction of crystalline CSH-phases, whereas geopolymer bodies maintain their strength. Implications for next generation concrete include that cement clinker could be completely replaced by using a using alkali silcate solution technology for gel formation.
Keywords
- Alkali-activated materials, Concretes, Geopolymer-gel, Lime-sand-brick
ASJC Scopus subject areas
- Chemical Engineering(all)
- Bioengineering
- Materials Science(all)
- Biomaterials
- Chemistry(all)
- Organic Chemistry
- Materials Science(all)
- Polymers and Plastics
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In: Gels, Vol. 8, No. 1, 9, 01.2022.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - The effect of gel-type contributions in lime-sand bricks, alkali-activated slags and CEMI/CEMIII pastes
T2 - Implications for next generation concretes
AU - Rüscher, Claus Henning
AU - Lohaus, Ludger
AU - Jirasit, Fongjan
AU - Tchakouté, Hervé Kouamo
N1 - Funding Information: C.H.R. and L.L. use LUH-internal support, F.J. by local support and H.K.T. by AvH.
PY - 2022/1
Y1 - 2022/1
N2 - Lime-sand bricks of different ages were investigated using IR-spectroscopy, thermogravimetry, and X-ray diffraction/scattering. After subtraction of the dominant quartz contribution (80%), the IR spectra show the absorption peaks of the hydrothermally formed binder phases. The spectra also show the alteration of the binder during ageing under atmospheric conditions by the influence of CO2 forming carbonate and a condensed SiO2-gel (secondary gel). The alteration could also be proven in X-ray pattern, obtaining a separation between crystalline CSH and amorphous contributions in the freshly produced lime-sand brick, too. Here, the formation of CSHamorph could be understood as a precursor state (primary gel) to the crystallization of CSH phases. X-ray patterns of aged bodies of alkali-silicate solution activated slags (AAS), CEM-I/CEM-III pastes, and CEM-I concrete indicate that in all cases a similar amorphous CSH-type phase (CSHamorph) was formed, which is responsible for the hardening properties as the glue. The main X-ray peak of CSHamorph obtained using CuKα-radiation with a usual diffractometer is observed between 24◦ and 35◦ 2 Theta with maximum at about 29◦ 2 Theta, whereas it appears much more broadly distributed between 15◦ and 35◦ 2 Theta with maximum between 26◦ and 28◦ 2 Theta for a geopolymer body prepared using the reaction of alkali-silicate solution and metakaolin (AAMK). This is due to the network formed by siloxo and sialate units in the case of AAMK, given that any crystallization can be ruled out. The origin of increasing mechanical strength during the ageing of AAS mortars must be due to further crosslinking of the preformed siloxo chains. Thermal treatment up to 800◦C leads to a complete loss of any mechanical strength of the CEM pastes due to the destruction of crystalline CSH-phases, whereas geopolymer bodies maintain their strength. Implications for next generation concrete include that cement clinker could be completely replaced by using a using alkali silcate solution technology for gel formation.
AB - Lime-sand bricks of different ages were investigated using IR-spectroscopy, thermogravimetry, and X-ray diffraction/scattering. After subtraction of the dominant quartz contribution (80%), the IR spectra show the absorption peaks of the hydrothermally formed binder phases. The spectra also show the alteration of the binder during ageing under atmospheric conditions by the influence of CO2 forming carbonate and a condensed SiO2-gel (secondary gel). The alteration could also be proven in X-ray pattern, obtaining a separation between crystalline CSH and amorphous contributions in the freshly produced lime-sand brick, too. Here, the formation of CSHamorph could be understood as a precursor state (primary gel) to the crystallization of CSH phases. X-ray patterns of aged bodies of alkali-silicate solution activated slags (AAS), CEM-I/CEM-III pastes, and CEM-I concrete indicate that in all cases a similar amorphous CSH-type phase (CSHamorph) was formed, which is responsible for the hardening properties as the glue. The main X-ray peak of CSHamorph obtained using CuKα-radiation with a usual diffractometer is observed between 24◦ and 35◦ 2 Theta with maximum at about 29◦ 2 Theta, whereas it appears much more broadly distributed between 15◦ and 35◦ 2 Theta with maximum between 26◦ and 28◦ 2 Theta for a geopolymer body prepared using the reaction of alkali-silicate solution and metakaolin (AAMK). This is due to the network formed by siloxo and sialate units in the case of AAMK, given that any crystallization can be ruled out. The origin of increasing mechanical strength during the ageing of AAS mortars must be due to further crosslinking of the preformed siloxo chains. Thermal treatment up to 800◦C leads to a complete loss of any mechanical strength of the CEM pastes due to the destruction of crystalline CSH-phases, whereas geopolymer bodies maintain their strength. Implications for next generation concrete include that cement clinker could be completely replaced by using a using alkali silcate solution technology for gel formation.
KW - Alkali-activated materials
KW - Concretes
KW - Geopolymer-gel
KW - Lime-sand-brick
UR - http://www.scopus.com/inward/record.url?scp=85121807793&partnerID=8YFLogxK
U2 - 10.3390/gels8010009
DO - 10.3390/gels8010009
M3 - Article
AN - SCOPUS:85121807793
VL - 8
JO - Gels
JF - Gels
IS - 1
M1 - 9
ER -