20.500.12556/DiRROS-28579 Alkali-activated materials from diverse solid precursors structural, mechanical and radiological properties This study investigates the gel characteristics of alkali-activated materials (AAMs) synthesized using wood ash (WA), and metakaolin (MK) as solid precursors. The research explores the influence of precursor type and sodium hydroxide (NaOH) concentrations in the alkali activator solution on the resulting physicochemical, microstructural, mechanical, and radiological properties of gels. The alkaline activators were prepared by mixing sodium hydroxide solutions (6 M and 12 M) with a sodium silicate (water glass) solution at a volume ratio of 1.5. The physicochemical characteristics of raw materials and AAMs were thoroughly analyzed using X-ray fluorescence (XRF), Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) with EDS elemental mapping. FTIR analysis confirmed the formation of an amorphous gels geopolymer network. XRD revealed the presence of characteristic crystalline phases (quartz, calcite) within an amorphous matrix. Mechanical properties, such as compressive strength, depended on precursor type and alkali molarity: metakaolin (12 M) reached ~14 MPa, while wood ash showed ~4 MPa (6 M) and ~0.5 MPa (12 M) due to high CaO, low Si and Al, and unfavorable SiO2/Al2O3 (5.71) and Na2O/Al2O3 (3.19) ratios. Furthermore, this research estimates radiological doses by quantifying radionuclide content via gamma-spectrometry. Alkali activation significantly reduced radiological haz- ard parameters, with radium equivalent activity (Raeq) decreasing to 238.0 Bq/kg and the external hazard index (Hex) to 0.643 for A12MK, while the annual effective dose rate for A12WA was only 0.265 nSv/y-all values remaining well below the recommended safety limit of 370 Bq/kg (≤1 mSv/y). The decrease in activity concentration index (Iγ), Raeq, and Hex with increasing NaOH concentration indicates effective radionuclide immobilization within the geopolymer matrix, confirming the suitability of these alkali-activated materials for safe use in construction from a radiation protection perspective. wood ash metakaolin alkali-activated materials radionuclides lesni pepel metakaolin alkalijsko-aktivirani materiali radionuklidi true false true MDPI AG Angleški jezik Slovenski jezik © 2026 by the authors Neznano 2026-03-24 13:24:03 2026-03-24 13:27:01 2026-03-27 03:47:19 0000-00-00 00:00:00 2026 0 0 str. 1-24 issue 3, [article no.] 200 Vol. 12 Feb. 2026 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2026-02-27 620.1/.2 2310-2861 10.3390/gels12030200 270957315 https://doi.org/10.3390/gels12030200 0 59c1679e-277c-11f1-aa40-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=42426 RAZ_Mladenovic_Nikolic_Natasa_2026.pdf RAZ_Mladenovic_Nikolic_Natasa_2026.pdf 1 A18239F62498D3696F977AEA927AF317 b9ecd67969cbb7f5cff209e530928a5b76fc4ac33d2e20f619459ffee3a38cae bb5e0b8c-277c-11f1-aa40-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=42428 Zavod za gradbeništvo Slovenije 0 0 0