Novel Radiation Shielding Concrete Utilizing Industrial Waste for Gamma-Ray Shielding

For the first time, the capability of red mud waste has been explored for the development of advanced synthetic radiation shielding aggregate and radiation shielding concrete. Red mud, an aluminium industry waste, consists of multicomponent and multi-elemental characteristics. Approximately two tons of red mud are generated for every ton of aluminium production. There are about 85 alumina plants all over the world, thus leading to the generation of about 77 million tons of highly alkaline waste annually. The major mineral content of red mud waste includes hematite, anatase, and cancrinite, thus making red mud waste the most suitable multicomponent resource material for developing multi phases containing shielding aggregate. Further, these multi-elements in the red mud are present in the form of oxide, oxy-hydroxide, and hydroxides, having low as well as high atomic number elements, namely sodium, iron, titanium compounds, respectively, and are non-toxic in nature. The concrete possessing specific gravity higher than 2600 kg/m3 is known as heavyweight concrete, and aggregate with specific gravities higher than 3000 kg/m3 is called heavyweight aggregate as per TS EN 206-1 (2002). The shielding aggregate contains both naturally occurring as well as some of the artificial aggregate. The natural aggregate includes hematite, magnetite, limonite barite, etc., which are nonreplenishable and are useful for many other important applications, and the artificial aggregate includes the use of iron shots and steel filing and in some cases, lead shots, etc. The use of lead shots makes the material toxic in nature, therefore, there is a need to avoid the use of lead-based materials for shielding applications, as it ranks second in the list of hazardous materials. Apart from toxicity associated with lead, the low melting point of lead is also prohibitive as the shielding concrete should be preferably heat and fire-resistant. Further, all the natural minerals inherently contain only a single shielding phase, therefore, conventionally shielding concretes are developed by a combination of various natural minerals, which leads to an inhomogeneous radiation shielding matrix in the developed conventional radiation shielding concrete. In view of the above, there is an urgent need to develop advanced non-toxic synthetic shielding aggregate capable of providing homogeneous radiation shielding matrix preferably obviating the use of toxic lead and conventional non-replenishable natural minerals resources. In this chapter, aluminium industrial waste, i.e., red mud, has been utilized. Chemical formulation and mineralogical designing of the red mud has been done by ceramic processing using appropriate reducing agents and additives. The chemical analysis, SEM microphotographs, and XRD analysis confirm the presence of multi-component, multi shielding, and multi-layered phases in developed advanced synthetic radiation shielding aggregate. The maximum density of developed synthetic aggregate is found to be 4.16 g/cc. The mechanical properties, namely aggregate impact value, aggregate crushing value, and aggregate abrasion value, have been evaluated and was compared with hematite ore aggregate and found to be an excellent material useful for making advanced radiation shielding concrete for the construction of nuclear power plants and other radiation installations.

For the first time, the development and design mix of novel radiation shielding concrete using innovative red mud-based synthetic shielding aggregates have been carried out in which the heavy density shielding aggregates are developed using red mud and are basically ceramic materials consisting of shielding phases, namely barium silicate (san-bornite), barium iron titanium silicate (bafertisite), barium aluminium silicate, iron titanium oxide (pseudorutile), barium titanate, barium iron titanium oxide, barium aluminium oxide, and magnetite, which are multi-elemental, multi phases, multi-layered crystal structures, therefore, they are excellent shielding materials.

The radiation shielding concrete was made using developed synthetic shielding aggregates adopting IS 10262-2009 standard for grade designation of M-30 concrete. The reference hematite ore concrete and developed concrete tested for radiation shielding attenuation properties for gamma rays using 137Cs (of photon energy 662 keV) and 241Am (of photon energy 60 keV) were found to possess highly effective shielding properties. The developed novel design mix concrete achieved an attenuation factor of 5.8 as compared to 5.1 attenuation factor for reference hematite ore concrete. The developed radiation shielding concrete using red mud-based synthetic shielding aggregates possess a broad application spectrum ranging from the construction of diagnostic X-ray, CT scanner rooms, and storing radioactive waste to nuclear power plants.

Keywords: Gamma-ray shielding, Radiation shielding concrete, Red mud.