2. Methods for measuring natural radioactivity in building materials

2.1 Conventional gamma-ray spectrometry

Usually, the three isotopes used to calculate the index are determined (by gamma spectrometry) on a sample. With this technique, the result obtained for index I shows a clear separation between the most common natural materials and those obtained by recycling from an industrial process: coal fly ash, phosphogypsum, blast furnace slag. Table 1 reproduces the values collected by the RP112 publication. It may be considered that if the unit index value is taken as the limit for unrestricted marking, recycled products cannot be freely marked on...