Determination of radon exhalation rate from different mixture of concrete

Indoor radon concentrations contribute significantly to the amount of natural radiation humans are exposed to and the choice of concrete mixture used in a building may influence the radon concentration indoor. Hence, this study evaluates the radon exhalation rate from different concrete mixtures. The concrete used comprises of a mixture of cement:coarse:fine aggregate, which was grouped as M10 (1:3:6), M15 (1:2:4), M20 (1:1.5:3), and M25 (1:1:2) from each of gravel and granite respectively. Each mixture was moulded into a rectangular prism of 130 mm × 80 mm × 80 mm, and sealed in an enclosed air-tight container for 28 days to attain secular equilibrium. The radon concentration (CRn) of each sample was thereafter measured with RAD7 detector, followed by the evaluation of the mass (Em) and surface (Es) exhalation rate. The results showed that M25 has the highest CRn for both the gravel and granite mixture with a value of 230.19 and 550.20 Bqm−3 respectively while M10 has the lowest CRn for both gravel (105.059 Bqm−3) and granite (175.098 Bqm−3). These values translate to the exhalation rate of M25 having the highest Em with 0.45 Bqkg−1h−1 for gravel and 1.08 Bqkg−1h−1 for granite, and the Es of M10 at 2.93 Bqm−2h−1 for gravel and 7.00 Bqm−2h−1 for granite compared with other groups. The Em and Es obtained in this work is however lower than the mean world value of 35 Bqkg−1h−1 and 57.6 Bqm−2h−1 respectively. Thus, radiologically, adequate ventilation should be provided when higher-strength concrete is used during building construction.