Optimization of reactive powder concrete by means of barite aggregate for both neutrons and gamma rays

High performance concrete has been often preferred in special engineering structures and in challenging composites products. Researchers have recently focused on the radiation shielding characteristics of these type concrete mixtures due to rising nuclear industry in the developing world. In the study, performance of reactive powder concrete was researched with regard to gamma-ray and neutron attenuation when its normal weight aggregate replaced with heavyweight aggregate (barite). For this purpose, reactive powder concrete mixtures were prepared 100% quartz aggregate, 100% barite aggregate and their blending 50–50%, by volume. Some physical and mechanical characteristics such as density, compressive strength, fracture energy, flexural strength and modulus of elasticity of the mixtures were determined. Gamma-ray attenuation coefficients and transmission thickness values were theoretically established for commonly known gamma energies (661.7, 1173.2 and 1332.5 keV). Optimization of the reactive powder mixtures was performed for both neutron and gamma-ray attenuation at 8 MeV. As a result, barite significantly increased the gamma-ray attenuation coefficients of reactive powder concrete. The mechanical performance of reactive powder concrete, however, was markedly reduced as a result of barite substitution. Replacement of quartz by barite aggregate has a more adverse impact on flexural strength than that of compressive strength. A mix that contains 40% barite aggregate of total aggregate volume was found as an optimum RPC mixture for simultaneously shielding neutrons and gamma rays. © 2018 Elsevier Lt

Properties of self-consolidating concrete incorporating coarse recycled concrete aggregate [Wlasciwosci betonu samozageszczajacego sie zawierajacego kruszywo grube z odpadowego betonu]

In this study, the effect of recycled concrete coarse aggregate on properties of self-consolidating concrete was examined. This aggregate was replacing 25%, 50%, 75%, 100% of limestone coarse aggregates. RC aggregate was used in SCC mixtures after 24 hours water saturation and surface dry (SSD). The results have shown that replacement of limestone coarse aggregate with RC aggregate caused the compressive strength decrease. However, the effect on tensile splitting and flexural strength was lower. As a result of this study it was found that it is possible to produce SCC compatible with EFNARC 2002. Moreover; it was observed that the use of RC aggregate in SSD state positively affected the fresh properties of SCC. © 2017, Foundation Cement, Lime, Concrete. All rights reserved.213M485The financial support of Scientific and Technical Research Council of Turkey (TUBITAK) under grant no. 213M485 is greatly acknowledged. -