Influence of the synthetic calcium aluminate hydrate and the mixture of calcium aluminate and silicate hydrates on the compressive strengths and the microstructure of metakaolin-based geopolymer cements

Moudio, Aimard Manfred Njawa; Tchakouté, Hervé K.; Ngnintedem, Dimace Lionel Vofo; Andreola, F.; Kamseu, Elie; Nanseu‐Njiki, Charles Péguy; Leonelli, Cristina; Rüscher, Claus H.

doi:10.1016/j.matchemphys.2021.124459

Cited by 21 publications

(10 citation statements)

References 36 publications

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“…Thus, a technology based on “alkali-activation” for gel formation could completely substitute the requirements of using alite and belite. At this point, we may refer to some investigations and more references therein concerning alternative sources substituting slag (H) for obtaining (Ca, Na, K)-poly(sialate-siloxo) networks as binders for sustainable building constructions, e.g., [ 16 , 17 ], and the effect of calcium phosphate compounds on the mechanical and microstructural properties of metakaolin-based geopolymers, e.g., [ 18 ]. Other directions of recent research concerning new binders for building construction are acid-based geopolymers, including calcined laterites [ 19 ].…”

Section: Discussionmentioning

confidence: 99%

The Effect of Gel-Type Contributions in Lime-Sand Bricks, Alkali-Activated Slags and CEMI/CEMIII Pastes: Implications for Next Generation Concretes

Rüscher

Lohaus

Jirasit

et al. 2021

Gels

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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.

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Section: Discussionmentioning

confidence: 99%

The Effect of Gel-Type Contributions in Lime-Sand Bricks, Alkali-Activated Slags and CEMI/CEMIII Pastes: Implications for Next Generation Concretes

Rüscher

Lohaus

Jirasit

et al. 2021

Gels

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“…Note that the small band located around 560−570 cm −1 is ascribed to the external linkage vibrations of the TO 4 in the double rings of zeolite. 44 The strongest absorbance peaks found in fully geopolymerized systems was assigned mainly to the asymmetric stretching vibrations of Si− O−T (T: tetrahedral Si or Al) in the N-A-S-H framework and is usually found between 800 and 1300 cm −1 in the FTIR spectrum. 45 Also, a shift in the Si−O−T peak toward the higher wavenumber is an indication of evolving geopolymerization.…”

Section: Xrd Tga and Ftir Analysismentioning

confidence: 99%

Preparation of Geopolymers with Nanosilica and Water-in-Air Pickering Emulsion: Mechanisms Underlying Its Rheology, Polymerization, and Strength

Yi,

Boluk,

Bindiganavile

2024

Langmuir

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Geopolymers are alkaline-activated aluminosilicate binders recognized as a promising alternative to traditional Portland cement due to their significantly lower greenhouse emissions, energy consumption, and carbon footprint. However, the challenge is meeting or exceeding the strength of Portland cement concrete while being prepared within a desired setting time and possessing workable rheology. A "water-in-air" Pickering emulsion, also called dry water, was prepared by stabilizing water droplets with hydrophobic nano silica and using them to control the geopolymer's strength, setting time, and workability. The mechanisms that underlie the effects of dry water on the rheology, setting, and strength were studied in detail through a combination of rheological, thermal, morphological, chemical, and microstructural assessments. A reduction in the viscosity and yield shear stress manifests in a higher flow diameter, principally due to the particle size coarsening in the precursor and the flowability of hydrophobic nano silica. There was a rapid rise in temperature during the setting process as the dry water temporarily increased the local alkalinity in the mixture, which boosted the dissolution of the precursor and, hence, the reaction. Outcomes from X-ray diffraction, thermogravimetric analysis, and Fourier-transform infrared confirm the highest degree of polycondensation for the principal N-A-S-H framework in mixtures containing dry water. These eventually correspond to a denser microstructure under scanning electron microscopy and, in turn, a superior mechanical strength. Depending on the unique combination of characteristics, including size coarsening, temporary water encapsulation, microfilling effect, and supplementary silica source, dry water resolves the "trade-off" between geopolymer's fresh and hardened properties when introducing nanoparticles.

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“…Tchakouté et al [5] investigated the effect of microcomposites on the compressive strength of geopolymer materials and obtained the maximum compressive strength of around 69 MPa when metakaolin was replaced by 10 wt% of microcomposite. The effects of calcium aluminate hydrate synthesis on the properties of metakaolin-based geopolymer composites were investigated by Moudio et al [6]. They concluded that when metakaolin is replaced by 10 wt% calcium aluminate hydrate, the maximum compressive strength of the final product is approximately 64 MPa.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Properties of Metakaolin-Based Geopolymer Materials Using Ferrisilicates as Additives Synthesised in Sodium Hydroxide Solution or Distilled Water

Tazune,

Nzangue,

Kamlo

et al. 2024

Engineering Science & Technology

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The main objective of this work is to investigate the behaviour of ferrisilicates prepared from hematite and two silica sources (rice husk ash and silica fume) on the compressive strength of geopolymer materials. Some ferrisilicates were synthesised in 2M sodium hydroxide solution. Others were prepared using distilled water as a solvent. The Fe2O3/SiO2 molar ratio contained in the ferrisilicates is set to 0.2. Metakaolin and sodium silicate solution with a molar ratio of SiO2/Na2O of 1.6 were used as the aluminosilicate and hardener in this work. The control geopolymer compressive strength is 53.34 MPa. For ferrisilicates prepared in alkaline solution using rice husk ash and silica fume, their compressive strength values are 71.91 and 77.72 MPa, respectively. The compressive strengths of the geopolymer materials made from ferrisilicates prepared in distilled water using rice husk ash and silica fume are 74.13 and 44.73 MPa, respectively. In the presence of ferrisilicate obtained by dissolving silica fume and hematite in sodium hydroxide solution, the maximum compressive strength of 77.72 MPa was obtained. When ferrisilicates from the mixture of silica fume, hematite, and distilled water are used as an additive, the minimum compressive strength of 43.73 MPa is achieved. It can be concluded that additives synthesised in an alkaline medium and those obtained in distilled water with rice husk ash improve compressive strength. On the other hand, the compressive strength of the geopolymer material that uses the additive produced with silica fume in distilled water is lower (44.73 MPa).

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Influence of the synthetic calcium aluminate hydrate and the mixture of calcium aluminate and silicate hydrates on the compressive strengths and the microstructure of metakaolin-based geopolymer cements

Cited by 21 publications

References 36 publications

The Effect of Gel-Type Contributions in Lime-Sand Bricks, Alkali-Activated Slags and CEMI/CEMIII Pastes: Implications for Next Generation Concretes

The Effect of Gel-Type Contributions in Lime-Sand Bricks, Alkali-Activated Slags and CEMI/CEMIII Pastes: Implications for Next Generation Concretes

Preparation of Geopolymers with Nanosilica and Water-in-Air Pickering Emulsion: Mechanisms Underlying Its Rheology, Polymerization, and Strength

Investigation of the Properties of Metakaolin-Based Geopolymer Materials Using Ferrisilicates as Additives Synthesised in Sodium Hydroxide Solution or Distilled Water

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