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Interaction of PCE and Chemically Modified Starch Admixtures with Metakaolin-Based Geopolymers—The Role of Activator Type and Concentration.

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Title: Interaction of PCE and Chemically Modified Starch Admixtures with Metakaolin-Based Geopolymers—The Role of Activator Type and Concentration.
Authors: Partschefeld, Stephan1 (AUTHOR) stephan.partschefeld@uni-weimar.de, Aschoff, Jasmine1 (AUTHOR), Osburg, Andrea1 (AUTHOR)
Source: Materials (1996-1944). Sep2025, Vol. 18 Issue 17, p4154. 28p.
Subjects: Starch, Dispersing agents, Plasticizers, Inorganic polymers, Chemical kinetics, Dispersion (Chemistry)
Abstract: Water-reducing admixtures are of enormous importance to adjust the workability of alkali-activated materials. Especially in geopolymers activated by highly concentrated alkaline solutions, the polycarboxylate ether (PCE) superplasticizers are less effective than in conventional cementitious systems. The aim of this study was to clarify the reasons for the lower dispersing performance of PCE and the synthesis of alternative dispersing agents based on the biopolymer starch to improve the workability of highly alkaline geopolymers. Furthermore, the focus of investigations was on the role of activator type and concentration as key parameters for geopolymer reaction and interaction of water-reducing agents. Therefore, in this study the conformation of three different types of PCE (MPEG: methacrylate ester, IPEG: isoprenol ether, and HPEG: methallyl ether) and synthesized starch admixtures in sodium and potassium hydroxide solutions (1 mol/L up to 8 mol/L) were studied. Furthermore, the dispersing performance, adsorption behavior, and influence on reaction kinetics in metakaolin-based geopolymer pastes were investigated in dependence on activator type and concentration. While the PCE superplasticizers show coiling and formation of insoluble aggregates at activator concentrations of 3 mol/L and 4 mol/L, the synthesized starch admixtures show no significant change in conformation. The cationic starch admixtures showed a higher dispersing performance in geopolymer pastes at all activator concentrations and types. The obtained adsorption isotherms depend strongly on the activator type and the charge density of the starch admixtures. The reaction kinetics of geopolymer pastes were not significantly influenced using the synthesized starch admixtures. Especially the cationic starch admixtures allow the reduction of liquid/solid ratios, which leads to higher flexural and compressive strengths. [ABSTRACT FROM AUTHOR]
Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Interaction of PCE and Chemically Modified Starch Admixtures with Metakaolin-Based Geopolymers—The Role of Activator Type and Concentration.
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  Data: <searchLink fieldCode="AR" term="%22Partschefeld%2C+Stephan%22">Partschefeld, Stephan</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> stephan.partschefeld@uni-weimar.de</i><br /><searchLink fieldCode="AR" term="%22Aschoff%2C+Jasmine%22">Aschoff, Jasmine</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Osburg%2C+Andrea%22">Osburg, Andrea</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Materials+%281996-1944%29%22">Materials (1996-1944)</searchLink>. Sep2025, Vol. 18 Issue 17, p4154. 28p.
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  Data: <searchLink fieldCode="DE" term="%22Starch%22">Starch</searchLink><br /><searchLink fieldCode="DE" term="%22Dispersing+agents%22">Dispersing agents</searchLink><br /><searchLink fieldCode="DE" term="%22Plasticizers%22">Plasticizers</searchLink><br /><searchLink fieldCode="DE" term="%22Inorganic+polymers%22">Inorganic polymers</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+kinetics%22">Chemical kinetics</searchLink><br /><searchLink fieldCode="DE" term="%22Dispersion+%28Chemistry%29%22">Dispersion (Chemistry)</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Water-reducing admixtures are of enormous importance to adjust the workability of alkali-activated materials. Especially in geopolymers activated by highly concentrated alkaline solutions, the polycarboxylate ether (PCE) superplasticizers are less effective than in conventional cementitious systems. The aim of this study was to clarify the reasons for the lower dispersing performance of PCE and the synthesis of alternative dispersing agents based on the biopolymer starch to improve the workability of highly alkaline geopolymers. Furthermore, the focus of investigations was on the role of activator type and concentration as key parameters for geopolymer reaction and interaction of water-reducing agents. Therefore, in this study the conformation of three different types of PCE (MPEG: methacrylate ester, IPEG: isoprenol ether, and HPEG: methallyl ether) and synthesized starch admixtures in sodium and potassium hydroxide solutions (1 mol/L up to 8 mol/L) were studied. Furthermore, the dispersing performance, adsorption behavior, and influence on reaction kinetics in metakaolin-based geopolymer pastes were investigated in dependence on activator type and concentration. While the PCE superplasticizers show coiling and formation of insoluble aggregates at activator concentrations of 3 mol/L and 4 mol/L, the synthesized starch admixtures show no significant change in conformation. The cationic starch admixtures showed a higher dispersing performance in geopolymer pastes at all activator concentrations and types. The obtained adsorption isotherms depend strongly on the activator type and the charge density of the starch admixtures. The reaction kinetics of geopolymer pastes were not significantly influenced using the synthesized starch admixtures. Especially the cationic starch admixtures allow the reduction of liquid/solid ratios, which leads to higher flexural and compressive strengths. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.3390/ma18174154
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      – Code: eng
        Text: English
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        StartPage: 4154
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      – SubjectFull: Starch
        Type: general
      – SubjectFull: Dispersing agents
        Type: general
      – SubjectFull: Plasticizers
        Type: general
      – SubjectFull: Inorganic polymers
        Type: general
      – SubjectFull: Chemical kinetics
        Type: general
      – SubjectFull: Dispersion (Chemistry)
        Type: general
    Titles:
      – TitleFull: Interaction of PCE and Chemically Modified Starch Admixtures with Metakaolin-Based Geopolymers—The Role of Activator Type and Concentration.
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            NameFull: Partschefeld, Stephan
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            NameFull: Aschoff, Jasmine
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            – D: 01
              M: 09
              Text: Sep2025
              Type: published
              Y: 2025
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