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Volume 18
Issue 21
10.3390/ma18214886
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety

by
Bahar Gharehpapagh
1,*,
Meike Denker
1,
Szymon Gadek
2,
Richard Gruhn
3,
Thomas Grab
3,
Kinga Korniejenko
2 and
Henning Zeidler
1
1
Institute for Machine Elements, Engineering Design and Manufacturing, Technische Universität Bergakademie Freiberg, 09599 Freiberg, Germany
2
Faculty of Materials Engineering and Physics, Cracow University of Technology, 31-155 Cracow, Poland
3
Scientific Diving Center, Technische Universität Bergakademie Freiberg, 09599 Freiberg, Germany
*
Author to whom correspondence should be addressed.
Materials 2025, 18(21), 4886; https://doi.org/10.3390/ma18214886 (registering DOI)
Submission received: 30 September 2025 / Revised: 20 October 2025 / Accepted: 22 October 2025 / Published: 24 October 2025
(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites (Second Edition))
Versions Notes

Abstract

Geopolymers are inorganic aluminosilicate binders formed by alkali activation of reactive powders, offering a sustainable, low-carbon alternative to Portland cement. Their rapid setting and chemical durability make them well-suited for additive manufacturing (AM) in demanding environments, including underwater construction, where chemical stability is essential for both structural integrity and environmental safety. This study evaluates two metakaolin-based formulations designed for underwater extrusion, differing in activator chemistry and rheology control. Standardized leaching tests revealed alkaline but stable leachates with strong immobilization of most ions; major anions and total dissolved solids remained within regulatory thresholds. Limited exceedances were observed—soluble organic carbon in the NaOH-activated mix and arsenic/selenium in the waterglass–sand system—highlighting specific areas for mix improvement rather than fundamental limitations of the material. Complementary radioactivity screening confirmed activity concentration indices well below the regulatory limit, with measured radionuclide activities falling comfortably within exemption ranges. Together, the leaching and radioactivity results demonstrate that both formulations provide robust matrix integrity and environmental compatibility, while highlighting clear opportunities for mix design improvements to further minimize ecological risks.
Keywords: geopolymers; additive manufacturing; environmental compatibility geopolymers; additive manufacturing; environmental compatibility

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MDPI and ACS Style

Gharehpapagh, B.; Denker, M.; Gadek, S.; Gruhn, R.; Grab, T.; Korniejenko, K.; Zeidler, H. Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety. Materials 2025, 18, 4886. https://doi.org/10.3390/ma18214886

AMA Style

Gharehpapagh B, Denker M, Gadek S, Gruhn R, Grab T, Korniejenko K, Zeidler H. Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety. Materials. 2025; 18(21):4886. https://doi.org/10.3390/ma18214886

Chicago/Turabian Style

Gharehpapagh, Bahar, Meike Denker, Szymon Gadek, Richard Gruhn, Thomas Grab, Kinga Korniejenko, and Henning Zeidler. 2025. "Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety" Materials 18, no. 21: 4886. https://doi.org/10.3390/ma18214886

APA Style

Gharehpapagh, B., Denker, M., Gadek, S., Gruhn, R., Grab, T., Korniejenko, K., & Zeidler, H. (2025). Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behavior, and Radiological Safety. Materials, 18(21), 4886. https://doi.org/10.3390/ma18214886

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