Radiological Aspects in the Evaluation of Portland Cements with Fine Aggregate Additions

The incorporation of recycled concrete fines (F), limestone (L), and ground granulated blast-furnace slag (S) as Portland cement constituents in accordance with EN 197-6 requires the determination of naturally occurring radionuclides to ensure radiological safety from a radiation protection standpoint. This study carried out a radiological assessment of eight cement types with varying proportions of L, F, and S additions, including anhydrous cements and mortars cured for 2 and 28 days. The activity concentrations of 226Ra, 232Th, and 40K were determined by gamma-ray spectrometry using HPGe detectors and radiochemical separation. In addition, the 222Rn emanation fractions were measured by the accumulation method using an AlphaGuard detector. Finally, annual effective doses were calculated using the RESRAD-BUILD software for a standard dwelling of 35 m2 occupied by an adult and an infant. Among the individual materials, S exhibited the highest activity in the uranium decay series (113 ± 24 Bq kg−1 of 238U), while L and F showed comparably lower values. Cements containing S additions (CEM II/C-M, CEM VI (S-L), and CEM VI (S-F)) were higher than the reference average value for building materials of 50 Bq kg−1, although all mortars remained below this value. Principal component analysis revealed significant correlations between S content, SiO2, Al2O3, and 232Th. The maximum annual effective dose reached 0.32 mSv for infants (CEM VI (S-L)), with the dose due to 222Rn inhalation being predominant. All cements studied are radiologically safe, confirming their suitability for use within the objectives of the circular economy.