By Nidhi DhullReviewed by Susha Cheriyedath, M.Sc.Sep 30 2024A recent article published in Scientific Reports investigated the impact of waste marble dust (MD) and granite dust (GD) on the radiation shielding properties of concrete, individually and in combination with nano alumina (NA), to enhance the concrete’s microstructure.
Study: Influence of sustainable waste granite, marble and nano-alumina additives on ordinary concretes: a physical, structural, and radiological study. Image Credit: Wongsakorn Dulyavit/Shutterstock.com
Background
Many industrial, medical, and nuclear fields use machines that produce artificial ionizing radiation such as X-rays and gamma-rays. Long-term and excessive exposure to such radiation can lead to nausea, vomiting, cancer, and, in extreme cases, death.
Thus, humans, animals, and the environment are all at risk from gamma/X-rays and neutrons, necessitating the development of materials for radiation attenuation and shielding.
Concrete, one of the most important building materials, is often used to absorb or distribute radiation. However, concrete consumes many natural resources, such as aggregates and water. Additionally, cement, an essential component of concrete, is environmentally expensive.
Consequently, several additives are used in concrete as supplementary cementitious materials (SCMs) to mitigate its environmental impact. Using waste materials like MD, GD, and NA as SCMs at optimal replacement ratios can improve the radiation-shielding properties of concrete against various radiation forms.
Methods
A concrete mix was prepared using type I ordinary Portland cement (OPC), sand as the fine aggregate, and crushed dolomite as the coarse aggregate. MD and GD, by-products generated by cutting, shaping, and polishing Karara marble and red granite, were sourced from ornamental stone factories in Shaq El-Thu’ban, Egypt, respectively.
These waste materials were processed into particles of less than 75 microns in size, making them suitable for cement replacement. Additionally, high-purity (>99%) NA particles with an average diameter of 20±5 nm were procured commercially.
Apart from a control mix, five blends (GMN) were designed using different SCMs individually and in combination based on the optimal replacement ratios identified from the literature. These included MD, GD, and NA at 6%, 6%, and 1%, respectively, and two blends with 1% NA each with MD and GD.
The prepared materials were characterized using X-ray fluorescence, energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Consequently, the waste dust’s microstructure, particle size, crystal structure, and mineralogical makeup were determined in various pure and mixed materials.
Radiation shielding measurements were performed using the Monte Carlo simulation (MCS) technique. The accuracy of the MCS model was confirmed with the Phy-X/PSD (photon shielding and dosimetry) program.
The radiation performance of the prepared materials was described using various attenuation coefficients. Notably, the neutron attenuation potential of the materials mentioned was determined by computing the fast neutron removal cross-section (FNRCS).
Results and Discussion
The prepared concrete specimens were effective radiation attenuators; the MCS and Phy software revealed the experimental and theoretical attenuation factors. Notably, the linear attenuation coefficient (µ) decreased with increasing gamma energy in all materials.
Due to their high densities, the GD+NA and MD+NA samples exhibited superior µ values than other concrete samples. This was attributed to the high atomic number of elements in GD/MD (Si, Al, Fe, etc.) and NA doping.
However, the likelihood of gamma absorption diminished while that of scattering increased with increasing photon energy range (Pγ). Additionally, with increasing Pγ, the material density, gamma interactions, and µ decreased.
The GMN-concrete samples exhibited higher µ values than the commercial concrete and glass (TZNNd9) samples. Moreover, the half-value layer thickness (H1/2) and tenth-value layer thickness (T1/10) of GMN-concrete samples increased with decreasing µ.
At low gamma-ray energy (0.015 MeV), all GMN-concrete samples had a radiation protection efficiency (RPE) of 100%. However, this value decreased sharply with increasing gamma-ray energy and penetrating strength.
Thus, the radiation energy governed the materials' radiation shielding efficiency. Additionally, one material might function more effectively than another at varying radiation energies.
The GD+NA sample exhibited maximum FNRCS efficiency, owing to the high concentration of light elements like oxygen and its high density. Moreover, the half-value and relaxation length corresponding to fast neutrons were the lowest for this sample. Notably, all six GMN-concrete samples exhibited good neutron shielding properties.
Conclusion
Overall, the researchers successfully used waste marble and granite combined with NA additives to improve ordinary concrete’s gamma-ray and neutron-shielding properties. The observed linear attenuation coefficient in different examined concrete mixes varied as ordinary concrete < MD < GD < NA < MD+NA < GD+NA.
The concrete mixes with the MD+NA and GD+NA samples exhibited the minimum H1/2, T1/10, and mean free path values. Additionally, the FNRCS of different concrete samples varied from 0.076 (for ordinary concrete) to 0.094 cm−1.
Thus, the prepared GMN-concrete samples offered the maximum protection against gamma rays and fast neutrons. Such material combinations with exceptional performance can enhance radiation shielding in nuclear and medical facilities.
Journal Reference
Mahmoud, A. A., El-Sayed, A. A., Aboraya, A. M., Fathy, I. N., Abouelnour, M. A., & Nabil, I. M. (2024). Influence of sustainable waste granite, marble and nano-alumina additives on ordinary concretes: a physical, structural, and radiological study. Scientific Reports, 14(1). DOI: 10.1038/s41598-024-72222-4. https://www.nature.com/articles/s41598-024-72222-4
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