Akademik Veri Yönetim Sistemi
JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY, cilt.335, sa.5, ss.3487-3500, 2026 (SCI-Expanded, Scopus)
The influence of fly ash incorporation on radon behavior in cementitious materials remains debated because studies rely on short-term measurements and indirect indicators. This work examines how replacement of Portland cement with Class F fly ash affects radon concentration above hardened cement pastes aged 150 days and how changes relate to mercury-intrusion parameters. Fly ash from the Tun & ccedil;bilek Thermal Power Plant, with elevated uranium and thorium content, was used to partially replace Portland cement at levels of 0, 5, 10, 15, 30, and 50 wt%. Prismatic specimens were tested by mercury intrusion porosimetry to obtain total porosity, intrusion volume, internal pore surface area, and characteristic pore diameters, while cylindrical specimens of the same mixes were subjected to radon concentration measurements using a DURRIDGE RAD7 detector in an open-loop configuration. Despite the higher radionuclide content of the fly ash, the radon concentration measured above the cement pastes decreased from 32.7 Bq/m3 for the 0% mixture to 17.5 Bq/m3 at 50% replacement, which is below the laboratory background level of 20 Bq/m3. Over the same range, total porosity increased from 13.9% to 19.1%, accompanied by higher intrusion volume and internal surface area, consistent with a more porous matrix with refined pore sizes and an altered pore network. These observations reveal a correlation between fly ash content, porosity characteristics, and reduced radon concentration under the tested conditions, suggesting that pore network refinement and increased internal surface area can mitigate radon release even when source radioactivity is higher. The study is restricted to a single high-radioactivity fly ash source, one specimen per mix, an age of 150 days, and a near-dry moisture state, without systematically exploring moisture variations, pore connectivity, or diffusion coefficients. Accordingly, the results should be interpreted as condition-specific correlations rather than a complete mechanistic description of radon transport.