Gamma-ray attenuation coefficients and transmission thickness of high consistency heavyweight concrete containing mineral admixture

WOS: 000442190700006In the study, high consistency heavyweight concrete mixtures containing barite aggregate were produced by using some common mineral admixtures (viscosity modifier, silica fume and fly ash) at various water/binder ratios and binder contents. Gamma-ray linear attenuation coefficients of the concrete mixtures were determined by using gamma sources of Cs-137 and Co-60 in NaI(Tl) gamma spectrometry system. The relationship between specimen thickness and transmission of the rays was constituted by emphasizing their mean free path, half-value layer, and tenth-value layer. Moreover, experimental mass attenuation coefficients of the concrete specimens were determined and compared with theoretical mass attenuation coefficients calculated by XCOM software depending on elemental fractions of these concrete in equivalent energies (662 keV, 1173 keV and 1332 keV). As a result, the replacement of the aforementioned admixtures with ordinary cement negatively affected the linear attenuation coefficients of the heavyweight concrete. A relative change of up to 25% was observed between the least and the highest attenuation thickness values at a certain gamma-ray transmission. A good regression relationship has been established between density and linear attenuation coefficients, density and mean free path, and density and half- or tenth-value layers of the heavyweight concrete. Theoretical (XCOM) mass attenuation coefficients were found similar to the experimental mass attenuation coefficients of the heavyweight concretes. Although there is a good linear regression relation between the theoretical and experimental mass attenuation coefficients at 662 keV energy of gamma rays, the relations were disappeared at 1173 and 1332 keV energies of gamma rays

Natural radioactivity of barite concrete shields containing commonly used supplementary materials

WOS: 000514758800011The recycling of hazardous materials within new composites has a sustainable importance as it contributes on the reduction of high radionuclide concentrations. in this study, the effect of cementitious materials i.e. viscosity modifier, silica fume and fly ash on the Ra-226, Th-232 and K-40 activity levels of barite concrete shields was researched by using different mixing compositions in terms of binder content, w/b ratio and the amount of supplementary cementitious materials. in comparison to cement, silica fume and fly ash used in the production of concrete shields were found to have significantly higher activity levels of K-40, as well as Ra-226, Th-232 and K-40, respectively. the Ra-226, Th-232 and K-40 activity levels of concrete shields range between 2.2 and 20.7 Bq kg(-1); 2.6 and 7.0 Bq kg(-1); 51.5 and 89.3 Bq kg(-1), respectively. These activity values were found similar or less than those of building materials in the world. These satisfactory results are mostly caused by the barite source which has lower radioactivity levels. the concrete mixture details used in the study caused significant variation in the natural radioactivity of barite concrete shields. the introduction of silica fume which has high K-40 activity levels and fly ash with high Ra-226, Th-232 and K-40 activity levels compared to cement and barite aggregate, significantly increased the radiological hazard parameters, although all results were found to be below the limits recommended by international reports. in conclusion. Ra-226 activity levels of the concrete shields were significantly increased (up to 8.4 times) by the variation of mix design parameters used in comparison with concrete mixtures that have the least Ra-226 activity level. the Th-232 and K-40 activity levels were as well increased in relatively less amounts (1.7 and 0.73 times higher, respectively). (C) 2019 Elsevier Ltd. All rights reserved