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- MakaleAçık Erişim2023Scopus SJRQ2Effect of elevated temperature on radiation shielding properties of cement and geopolymer mortars including barite aggregate and colemanite powder
Kök, S.; Türetken, M.S.; Öksüzer, N.; Gökçe, H.S.
This study aims to investigate the radiation shielding efficiency of cement and geopolymer-based mortars after exposure to elevated temperatures which may happen during the activation process of nuclear reactors. To contribute to the shielding properties, these binders were modified with the substitution of colemanite powder (5 and 10%), and barite aggregate was used to be an alternative to silica sand, as well. The produced specimens were exposed to 300 and 500 °C. While the colemanite powder resulted in significant retardation of setting time up to 183% for cement-based series, a set accelerator effect reaching 67% was found in the geopolymer series. Unlike expectation, the losses in mechanical and shielding properties have become more pronounced in geopolymer mortars at the applied temperatures. In particular, a significant increase reaching 28% in compressive strength of cement series was found after 300 °C exposure. It was noted that cement series with reaching a linear attenuation coefficient of 0.162 cm−1 presented more effective shielding against gamma rays when compared to that (0.134 cm−1) of geopolymers. To moderate thermal neutrons, geopolymer series reaching a linear attenuation factor of 2.799 cm−1, were found to be a more promising alternative according to cement series reaching 2.140 cm−1.
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İncele - MakaleAçık Erişim2018Scopus SJRQ1Gamma-ray attenuation coefficients and transmission thickness of high consistency heavyweight concrete containing mineral admixture
Gökçe, H.Süleyman; Öztürk, Buket Canbaz; Çam, N.Füsun; Andiç-Çakır, Özge
In 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 137Cs and 60Co 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.
AtıfScopus185WoS173OpenAlex193İncele