{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T04:54:18Z","timestamp":1787028858072,"version":"build-2736575974"},"reference-count":45,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2025,10,24]],"date-time":"2025-10-24T00:00:00Z","timestamp":1761264000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Saxon State Parliament"},{"DOI":"10.13039\/501100005632","name":"National Centre for Research and Development","doi-asserted-by":"crossref","award":["M-ERA. NET3\/2021\/71\/MARWRECK\/2022"],"award-info":[{"award-number":["M-ERA. NET3\/2021\/71\/MARWRECK\/2022"]}],"id":[{"id":"10.13039\/501100005632","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>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\u2014soluble organic carbon in the NaOH-activated mix and arsenic\/selenium in the waterglass\u2013sand system\u2014highlighting 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.<\/jats:p>","DOI":"10.3390\/ma18214886","type":"journal-article","created":{"date-parts":[[2025,10,29]],"date-time":"2025-10-29T04:26:29Z","timestamp":1761711989000},"page":"4886","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Geopolymer Materials for Additive Manufacturing: Chemical Stability, Leaching Behaviour, and Radiological Safety"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3771-4344","authenticated-orcid":false,"given":"Bahar","family":"Gharehpapagh","sequence":"first","affiliation":[{"name":"Institute for Machine Elements, Engineering Design and Manufacturing, Technische Universit\u00e4t Bergakademie Freiberg, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Meike","family":"Denker","sequence":"additional","affiliation":[{"name":"Institute for Machine Elements, Engineering Design and Manufacturing, Technische Universit\u00e4t Bergakademie Freiberg, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Szymon","family":"Gadek","sequence":"additional","affiliation":[{"name":"Faculty of Materials Engineering and Physics, Cracow University of Technology, 31-155 Cracow, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard","family":"Gruhn","sequence":"additional","affiliation":[{"name":"Scientific Diving Center, Technische Universit\u00e4t Bergakademie Freiberg, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4235-5494","authenticated-orcid":false,"given":"Thomas","family":"Grab","sequence":"additional","affiliation":[{"name":"Scientific Diving Center, Technische Universit\u00e4t Bergakademie Freiberg, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8265-3982","authenticated-orcid":false,"given":"Kinga","family":"Korniejenko","sequence":"additional","affiliation":[{"name":"Faculty of Materials Engineering and Physics, Cracow University of Technology, 31-155 Cracow, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0800-9678","authenticated-orcid":false,"given":"Henning","family":"Zeidler","sequence":"additional","affiliation":[{"name":"Institute for Machine Elements, Engineering Design and Manufacturing, Technische Universit\u00e4t Bergakademie Freiberg, 09599 Freiberg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"106592","DOI":"10.1016\/j.resconrec.2022.106592","article-title":"A sustainable roadmap for additive manufacturing using geopolymers in construction industry","volume":"186","author":"Raza","year":"2022","journal-title":"Resour. 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