The manufacture of Portland cement entails high energy and environmental costs, and various solutions have been implemented in recent years to mitigate this negative impact. These solutions include improvements in the manufacture of cement clinker or the use of supplementary cementitious materials (SCMs), such as fly ash (FA) or slag as a replacement for a portion of the clinker in cement. The incorporation of these SCMs in cement may increase its radiological content as they are naturally occurring radioactive materials (NORMs). The Activity Concentration Index (ACI) is a screening tool established in the European EURATOM Directive 2013/59 to determine the radiation protection suitability of a final construction material. The ACI is determined by the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, usually determined by gamma spectrometry. The methodology of gamma spectrometry is accurate and appropriate, but this technique is not available in all laboratories. For this reason, and taking into account that there is a relationship between the chemical and radiological composition of these building materials, a new approach is proposed to determine the radiological content of these materials from a chemical analysis such as X-ray fluorescence (XRF). In this paper, principal component analysis (PCA) is used to establish the relationships between the chemical composition and radiological content of cements, FAs, and slags of different natures. Through PCA it was possible to group the cements based on two variables: CaO content and Fe₂O_3–Al₂O_3–TiO₂ content. A lower correlation was observed for the FAs and slags, as the sample scores were centered around the origin of the coordinates and showed greater dispersion than the cements. The clusters obtained in the HJ–Biplots allowed the determination, using multiple regression, of models relating the activity concentration of ²²⁶Ra, ²³²Th (²¹²Pb), and ⁴⁰K to the oxide percentages obtained for the three matrices studied. The models were validated using five cements, one FA and one slag with relative percentage deviations (RSD(%)) equal to or less than 30% for 89% of the activity concentrations and 100% of the ACI determined.

This database is a useful tool in the construction industry, ensuring that building materials comply not only with technical standards but also with radiation safety regulations. In the past few years, the cement industry has used so-called SCMs to reduce the carbon footprint of cements, without considering that these SCMs (supplementary cementitious materials) are mostly NORMs (Naturally Occurring Radioactive Materials) that may contain variable levels of radionuclides, primarily ²²⁶Ra (of the ²³⁸U series), ²³²Th and ⁴⁰K. These levels must be controlled in the final construction product, as required by regulations (EU Directive 2013/59). This paper presents data on the activity concentration of natural radionuclides in cements, SCMs, aggregates, and mining and ceramic wastes that are likely to be used as SCMs in the future. Specifically, it presents the chemical composition of these materials alongside with their radionuclide activity concentration data obtained by gamma spectroscopy. These results serve as a database that can be used in different studies to assess the possibility of using these materials in construction materials in compliance with European regulations on radiation protection.

The radiological characterization of aggregates used in construction materials is essential to determine their suitability from a radiological protection perspective and to ensure their safety for health and the environment. While the activity concentrations of radionuclides present in construction materials are typically determined using gamma spectrometry, an alternative approach involves the development of statistical methods and predictive models derived from the chemical composition of the material. A total of 39 aggregates used in construction of various types (siliceous, carbonatic, volcanic, and granitic) have been analyzed, correlating their chemical compositions obtained through X-ray fluorescence (XRF) with the activity concentrations of natural radionuclides measured via gamma spectrometry using principal component analysis (PCA). The results obtained allowed for the observation of an inversely proportional relationship between the chemical composition of the grouping of siliceous and carbonatic aggregates and the content of radionuclides. However, the set of granitic aggregates showed a strong correlation with the natural radioactive series of uranium, thorium, and ⁴⁰K. Conversely, the radionuclide content of volcanic aggregates was independent of their chemical composition. The results obtained from the PCA facilitated the development of different models using multiple regression analysis. The chemical parameters obtained in the proposed models were related to the typical mineralogy in each grouping, ranging from primary minerals such as feldspars to accessory minerals such as anatase, apatite, and pyrolusite. Finally, the models were validated using independent samples from those used to determine the models, achieving RSD (%) values ≤ 30% in 50% of the activity concentrations of ²²⁶Ra, ²³²Th(²¹²Pb), and ⁴⁰K, as well as the estimated ACI.