Natural radioactivity, radon exhalation rate in stony materials and radon diffusion coefficient in waterproofing materials

In the present study, natural radioactivity and radon exhalation rates of 55 stony material samples divided into three groups (Gneiss, Granite and Marble) were estimated by means of laboratory tests. The activity concentration range was found: 5.5 +/- 1.3-125.5 +/- 6.5 Bq.kg-1 for 226Ra, 4.4 +/- 0.6-157.4 +/- 8.4 Bq.kg-1 for 232Th and 35.0 +/- 0.4-1093 +/- 15 Bq.kg-1 for 40K. The data were used to evaluate radiation hazard parameters. The radon exhalation rate ranged from 0.17 +/- 0.01 to 2.56 +/- 0.20 Bq.m-2.h-1. Granite building materials show the highest radon exhalation rates while the marble group shows the lowest exhalation rates. Positive correlation coefficients of radon exhalation rate with radium concentration and porosity of the samples have been observed. This study also presents radon diffusion coefficient values determined for 50 waterproofing materials. A radon-proof ability comparison of waterproofing materials and a conclusion about material groups which can be considered very effective radon barriers were discussed.