Utilization of garnet residue in radiation shielding cement mortar

Highlights

• Garnet residue is utilized as sand replacement at 25–100% in cement mortar.

• Mortar incorporating 100% garnet residue exhibited the highest density and compressive strength.

• Gamma-ray and neutron transmissions decreased with increasing garnet residue ratios.

Abstract

This experimental investigation was carried out to evaluate the potential of garnet residue, a by-product from the abrasive industry, as an aggregate in cement mortar through the physical, mechanical, microstructure, leaching and radiological properties. The findings revealed that the sand replacement by garnet residue enhanced the physical and mechanical properties. In radiological experiments, the cement mortar incorporating garnet residue at 100% by weight improved both gamma-ray and neutron shielding properties at 34% and 26%, respectively, better than the control sample. Thus, based on these results, it is concluded that the percentage of garnet residue can fully replace sand in radiation shielding cement mortar.

Introduction

With increasing nuclear applications, such as nuclear research and medical diagnostic centers, power reactors, and high-energy particle accelerators, the protection against nuclear radiation becomes very important for avoiding the harmful effects on human health and the environment [1], [2]. High-density concrete is well known and has been widely used as radiation shielding for many years, due to its properties and it can be prepared from a variety of materials and methods. To produce high-density concrete for radiation shielding, the heavy aggregates, such as magnetite [3], [4], [5], hematite [6], limonite [7], [8], colemanite [9] and barite [10], [11], are utilized, to gain concrete densities of approximately 2600–4500 kg/m³. In concrete mixes designed for radiation shielding, the most considerable rays are gamma and neutron. In many cases, the high-density concretes from these heavy aggregates preferred potential to attenuate the gamma-rays rather than the neutrons, due to the aggregates containing no elements with a high neutron capture cross-section. The finding was concurred by Akkurt and El-khayatt [12]. They conducted a study using high-density concrete made from barite to be the neutron and gamma-ray barrier. They noted that barite was more effective on gamma-ray shielding rather than neutron shielding.

Typically, concrete can partly absorb neutrons due to the hydrogen contained in it (approximately 1% unit weight) [13]. To improve the shielding property against both gamma-rays and neutrons, this could be obtained by mixed hydrogenous materials, heavy metal elements and other neutron absorbers [12]. Roslan et al. [14], utilized ferro boron with granite as coarse aggregates to prepare high-density concrete. They concluded that the gamma-rays are attenuated by concrete density, whereas neutron transmission is influenced more by the ferro boron content in concrete. Kharita [15] proposed that the hematite concrete contributed to its high density for gamma shielding and the presence of the high content of iron and iron hydroxide for neutron shielding.

In recent years, there have been some research studies that have utilized industrial by-products or wastes, such as lead mine, iron slag, electric arc furnace slag and steel shot, as a substitute for conventional aggregate in radiation shielding concrete. These by-products or wastes have been pronounced to not only reduce costs and waste to landfills, but also as alternative materials for radiation shielding concrete. Cullu and Ertas [16] prepared lead mine waste concrete to attenuate the gamma-rays, and noted that the linear attenuation coefficient decreased due to an increasing amount of lead mine waste. Maslehuddin et al. [17] also revealed that the use of 50% of electric arc furnace and 50% of steel shot as coarse aggregate could meet the weight and radiation requirements. Ouda et al. [18] showed that sand replacement by iron slag at 100% by weight in cement mortar gave the highest strength, density and gamma-ray shielding efficiency. This indicated that iron slag can fully replace sand in cement mortar.

In this investigation, garnet residue, a by-product from the abrasive industry, was applied and utilized as an alternative cheaper material in radiation shielding concrete. The main objective of this investigation was to study the effect of sand replacement by garnet residues at various percentages (25–100%) on the physical, mechanical, microstructure, leaching and radiological properties of cement mortar. In regard to the radiological property, the study aimed to investigate the attenuating capacity of garnet residue on both neutrons and gamma-rays.