The Variable Frequency Conductivity of Geopolymers during the Long Agieng Period

Walter, Janusz; Uthayakumar, M.; Balamurugan, P.; Mierzwiński, Dariusz

doi:10.3390/ma14195648

Cited by 5 publications

(3 citation statements)

References 36 publications

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“…Gelation and vitrification, two macroscopic phenomena encountered during this process, strongly alter the viscoelastic behaviour of the material in these early phases of the geopolymerization stages. For long-term property changes, other methods such as variable frequency conductivity, XRD qualitative and quantitative analysis, porosity measurements, and sorption analysis were applied to characterise the process of solidification of geopolymers based on fly ash with sand additives [31,[47][48][49][50][51][52].…”

Section: Discussionmentioning

confidence: 99%

Chemorheology of a Si/Al > 3 Alkali Activated Metakaolin Paste through Parallel Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA)

Aversa,

Ricciotti,

Perrotta

et al. 2023

Polymers

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Although geopolymers, as structural materials, should have superior engineering properties than traditional cementitious materials, they often need to improve their final characteristics’ reproducibility due to the need for more control of the complex silico-aluminate decomposition and polymerisation stages. Thermosetting of a reactive geopolymeric paste involves tetrahedral Silicate and Aluminate precursor condensation into polyfunctional oligomers of progressively higher molecular weight, transforming the initial liquid into a gel and a structural solid. Viscosity and gelation control become particularly critical when the geopolymer is processed with 3D printing additive technology. Its physical state modification kinetics should match the flow and setting characteristics required by the deposition process. The reaction kinetics and the elastic and viscous characteristics preceding gelation and hardening have been investigated for an alkali-activated Metakaolin/Sodium Silicate-Sodium Hydroxide paste with a Si/Al ratio > 3. A chemoreological approach has been extended to these inorganic polymerisable systems, as already utilised for organic thermosetting polymers. Differential scanning calorimetry and Oscillatory DMA were carried out to monitor the advancement of the polymerisation reaction and the associated variations of the rheological viscoelastic properties. Dynamic thermal scans were run at 1 °C/min and a frequency of 10 Hz for the dynamic mechanical tests. The observed kinetics of polymerisation and variations of the elastic and viscous components of the complex viscosities and shear moduli are described in terms of polycondensation of linear and branched chains of oligomeric macromolecules of increasing complexity and molecular weight up to gelation (Gel1) and cross-linking of the gelled macrostructure (Gel2) and final glassy state. Geopolymerization can be allocated into two main behavioural zones: a viscoelastic liquid paste below 32.5% of reaction advancement and a viscoelastic solid above. Initial complex viscosities range from 2.3 ± 0.9 × 10−5 MPa*s to 6.8 ± 0.9 × 10−2 in the liquid-like state and from 1.9 ± 0.1 MPa to 9.6 ± 2.1 × 102 MPa in the solid-like state.

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Section: Discussionmentioning

confidence: 99%

Chemorheology of a Si/Al > 3 Alkali Activated Metakaolin Paste through Parallel Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA)

Aversa,

Ricciotti,

Perrotta

et al. 2023

Polymers

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“…This type of fly ash contains many spherical particles [24]. Metakaolin contains many silicon oxides and aluminum oxides [25][26][27]. Qualitative analysis of the elemental composition of the examined surfaces showed elements in clay brick and concrete waste (rubble) such as oxygen, silicon, aluminum, iron and-in the case of concrete waste-calcium.…”

Section: Methodsmentioning

confidence: 99%

Investigation of Mechanical Properties and Microstructure of Construction- and Demolition-Waste-Based Geopolymers

et al. 2022

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Construction and demolition waste (CDW) is the third-most abundant waste generated annually in the countries of the European Union. One of the alternatives to the use of these wastes is geopolymeric materials. Partial replacement of commonly used raw materials for the production of these materials can help reduce the number of landfills and the consumption of natural resources. In this study, the authors partially replaced metakaolin and fly ash with clay bricks and concrete debris. The research method in article is connected with analysis of microstructures and the mechanical and physical properties of the geopolymers. The results obtained show the possibility of manufacturing useful construction materials based on industrial byproducts (fly ash) and CDW. Compressive strength and flexural strength were, for samples containing metakaolin, 20.1 MPa and 5.3 MPa, respectively. Geopolymers containing fly ash displayed 19.7 MPa of compressive strength and 3.0 MPa of flexural strength. The results for both synthesized materials give them perspectives for future applications in the construction industry.

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“…We applied a method based on impedance measurements using changing frequency and current, known as EIS (electrochemical impedance spectroscopy) [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”

Section: Introductionmentioning

confidence: 99%

Possibilities of Checking Water Content in Porous Geopolymer Materials Using Impedance Spectroscopy Methods

Mierzwiński,

Walter,

Wanat

2023

Materials

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The porous geopolymer has been tested for its content of water using impedance methods. The pores of the material were filled with distilled water using a desiccator and a vacuum pump. An analysis of differential scanning calorimetry (DSC) was carried out in the next step to check the content of water, porosity and approximate value of specific heat of the geopolymer. Additionally, mercury porosimeter has been used for checking the porosity. The geopolymer material characterized in this way was subjected to impedance tests aimed at developing a quick method for assessing the water content in the material. Impedance measurements have been realized on an electrochemical workstation applying a 50 mV non-destructive amplitude of the potential and a frequency range of 1 Hz to 100 kHz. Change in the module of impedance and the phase shift angle were measured while the material was dried out. Significant differences were observed. The obtained graphs were simulated using a schematic model consisting of constant phase elements (CPEs) and a resistor (R). These values showed mechanisms of charge conduction. A simple method for assessing the water content of a porous geopolymer has been proposed in this paper. The real and imaginary impedance values were shown in Nyquist graphs. These graphs have characteristic maxima that move according to a linear equation with decreasing water content. Changes in Nyqiust charts are clearly visible even with small changes in the water content of the material and can be very useful for assessing it.

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The Variable Frequency Conductivity of Geopolymers during the Long Agieng Period

Cited by 5 publications

References 36 publications

Chemorheology of a Si/Al > 3 Alkali Activated Metakaolin Paste through Parallel Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA)

Chemorheology of a Si/Al > 3 Alkali Activated Metakaolin Paste through Parallel Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA)

Investigation of Mechanical Properties and Microstructure of Construction- and Demolition-Waste-Based Geopolymers

Possibilities of Checking Water Content in Porous Geopolymer Materials Using Impedance Spectroscopy Methods

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