Naturally occurring radioactivity in some Swedish concretes and their constituents – Assessment by using I-index and dose-model
Section snippets
European regulations and directives
The European Commission (2014) recently declared, through the implementation of the EU's Basic Safety Standard (BSS), a reference level for dose from gamma radiation in building materials from the natural radioisotopes 40K, 226Ra (238U) and 232Th. The Construction Product Regulation, CPR (CE, 2011) views the building materials as construction products, including materials such as concrete. Hence, a construction product can have several constituents of different building materials. It is also
Laboratory gamma spectrometric analyses (STUK)
The methodology to compare different products, such as aggregates, cement and concrete was based on the laboratory analytical procedure described in Draft TS 00351014 (2012), using gamma-spectrometry to analyze activity concentrations of naturally occurring radionuclides. The Swedish Cement and Concrete Research Institute (CBI) has consulted the Radiation and Nuclear Safety Authority of Finland (STUK) that uses this methodology (Klemola et al., 2010) as an accredited test method.
The gamma
Results
Table 2 shows the gamma spectrometric analyses for the aggregates, water, additive, cement and concrete. The thickness of the concrete castings and the density of the aggregates are also included in the Table. The type of method is indicated in the “sample type” column, where A = crushed aggregate, A-S=Aggregate, natural sand, Amix = 2–3 aggregate particle size fractions combined according to the recipe and sent for analysis, Aw = mean value (wt%), calculated by CBI from single aggregate
Analysis and discussion
The approach of the paper was to emphasize the differences in radiation dose between a construction/building material (concrete) and its constituents (e.g. aggregate). There are, however, some uncertainties that need to be addressed. Sample four (Id-number 4) showed a significantly higher thorium content as part of the concrete samples, than in the aggregates (Table 2, Fig. 1). The concrete samples analyses were repeated three times for the concrete specimen of 150 mm and twice for the concrete
Concluding remarks
Aggregates used in concrete and the concrete containing the aggregates were empirically examined by laboratory gamma ray spectrometry. The calculated R2-values of the regression analysis of Fig. 1, Fig. 2, excluding sample 4, yield R2-values >0.95, are interpreted as trustworthy correlations in the linear regression models.
Calculations of I-indices of the aggregates and their respective concrete mix show an overall approximate decrease of the gamma radiation by 16–19%, when the aggregate is
Acknowledgments
Special thanks to the Swedish Consortium for Financing Fundamental Research in the Concrete Area, who has partly funded and supported the research and the project using empirical data. Specially thanks also to some native English speaking colleagues at Borås, who have assisted in the first critical review of the document in English with great patience. Finally, the authors wish to express their utmost appreciations to the colleagues at CBI Borås, who have contributed with strong efforts to cast
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