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<p>This study investigates the influence of partial replacement of ordinary Portland cement with limestone from three distinct geological sources at substitution levels of 5–20 Wt. %. The effects on hydration kinetics and phase composition were systematically evaluated over curing periods of 3, 7, 28, and 90&#xa0;days. The water demand, setting time, chemically bound water, bulk density, total porosity, free lime, and compressive strength were evaluated. Differential thermal analysis and X-ray diffraction were employed to characterize hydration products and phase identification. Results indicated that both limestone replacement levels and source significantly influenced hydration behavior and mechanical performance. Alexandria limestone, particularly at replacement levels of 5 to 10%, enhanced hydration kinetics in the early ages and compressive strength due to favorable particle properties and nucleation effects, while El-Menia limestone showed a higher long-term chemically bound water content, indicating a greater overall degree of hydration at extended treatment lifetimes. In contrast, Helwan limestone showed reduced performance at higher substitution levels, likely due to its coarser texture and lower reactivity. Furthermore, the gamma ray attenuation and neutron shielding performance were significantly influenced by the mixture composition. Alexandria mixtures (Ax5 and Ax10) exhibited the highest linear attenuation coefficients (LAC), lowest half-value layers (HVL), and highest radiation protection efficiency (RPE), particularly at 0.662, 1.17, and 1.33&#xa0;MeV. Neutron shielding showed a similar trend, with Alexandria mixtures achieving superior macroscopic neutron cross-section, confirming their suitability for multi-functional structural and shielding purposes.</p>

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Towards sustainable radiation protection: hydration, gamma-ray, and neutron shielding of OPC–limestone composites from diverse geological origins

  • 期刊论文

  • 发表日期：

    2026年1月17日

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  • Ahmed S. Ouda

摘要

This study investigates the influence of partial replacement of ordinary Portland cement with limestone from three distinct geological sources at substitution levels of 5–20 Wt. %. The effects on hydration kinetics and phase composition were systematically evaluated over curing periods of 3, 7, 28, and 90 days. The water demand, setting time, chemically bound water, bulk density, total porosity, free lime, and compressive strength were evaluated. Differential thermal analysis and X-ray diffraction were employed to characterize hydration products and phase identification. Results indicated that both limestone replacement levels and source significantly influenced hydration behavior and mechanical performance. Alexandria limestone, particularly at replacement levels of 5 to 10%, enhanced hydration kinetics in the early ages and compressive strength due to favorable particle properties and nucleation effects, while El-Menia limestone showed a higher long-term chemically bound water content, indicating a greater overall degree of hydration at extended treatment lifetimes. In contrast, Helwan limestone showed reduced performance at higher substitution levels, likely due to its coarser texture and lower reactivity. Furthermore, the gamma ray attenuation and neutron shielding performance were significantly influenced by the mixture composition. Alexandria mixtures (Ax5 and Ax10) exhibited the highest linear attenuation coefficients (LAC), lowest half-value layers (HVL), and highest radiation protection efficiency (RPE), particularly at 0.662, 1.17, and 1.33 MeV. Neutron shielding showed a similar trend, with Alexandria mixtures achieving superior macroscopic neutron cross-section, confirming their suitability for multi-functional structural and shielding purposes.