Design and optimization of heavy-weight concrete compositions for the fields with different degrees of ionizing radiation
The aim of corresponding reaserch activities is to develop heavy-weight concrete with shielding properties against ionizing radiation, which could be used in nuclear plants, for medical units, particle accelerator facilities or storage bunkers of nuclear wastes. In such massive concrete structures, it is very important to decrease the possilibility of thermal cracking, to ensure volumetric stability, low permeability and associated sufficient mechanical properties. Exothermic hydration reactions of cement binders thus play a key role. They can generate fast temperature rise in the core of the concrete structure leading to the temperature difference with the surface parts. As consequence of a non-uniform heat distribution and thermal conductivity, the temperature gradient will cause tensile stress.
Concrete design must also take into consideration the presence of radioactive isotopes, in order to minimize the activation effect of gamma and neutron radiations. Therefore, chemical composition of individual constituents is decise.
To accomplish all the requirements, the following partial goals have to be fulfilled:
• evaluation of chemical composition of selected high density aggregates and cementitious binders using Neutron Activation Analysis, Prompt-Gamma Activation Analysis, and Energy Dispersive X-ray Fluorescence methods to provide complete knowledge on elemental composition including isotopes,
• selection of the suitable heavyweight aggregate (baryte, magnetite or their combination, cast iron),
• optimization of multicomponent binder composition composed of Portland cement and additives (silica fume, metakaolin, and ground granulated blast-furnace slag) based on their chemical composition and generated hydration heat,
• evaluation of engineering properties of optimized heavy-weight concretes.
Fig.1. TG/DTG curves (left) and Dynamic moduli of elasticity of heavy-weight concrete samples (right).