Does the utilization of coal fly ash in concrete construction present a radiation hazard?

The advantages of utilization of coal fly ash in concrete construction, as well as the technological and environmental problems caused by an elevated content of chemical/radioactive contaminants, are discussed. The paper deals with the question whether the utilization of coal fly ash in concrete construction presents a radiation hazard. The analysis of the experimental studies shows that although radon exhalation rate of concrete containing coal fly ash can be sometimes slightly higher, than that of the reference concrete, radon emanation coefficient is lower. In view of this, the standards regulating radioactivity of building materials, but not addressing the decrease of radon emanation coefficient properly could be detrimental to the utilization of fly ash in concrete construction. Drawing direct comparisons between results presented in different papers is challenging because of varying methodologies, sample sizes, material properties, such as age, moisture and porosity, and experimental goals. The need in the systematic study considering different factors, which can influence the radon release of a concrete, is emphasized.