Effect of using heavy chemical additives on the mechanical properties of cement pastes, radiation exposure and the corrosion behavior of reinforced steel upon exposure to sea water

The current study aims to explore the impact of lead oxide and lead phosphate on the attenuation coefficient of concrete used as radiation shielding in nuclear facilities, the physico-mechanical properties of cement pastes, and the corrosion behavior of reinforced steel when exposed to seawater. The mixtures were prepared upon partial replacement of Portland cement with lead oxide and lead phosphate at levels ranging from 0.1% to 0.5%, by mass. The physico-mechanical properties of cement pastes were examined. Gamma transmission parameters were measured, as was the effective removal-cross-section (Sigma R) of fast neutron spectra, while the corrosion behavior of embedded steel reinforcement upon exposure to sea water was measured. Results indicated that In comparison to the reference OPC sample at early ages, the compressive strength value of the hardened cement pastes decreases with increasing lead oxide and lead phosphate content. but at 28 and 90 days, the hardened cement paste's compressive strength values increase as lead oxide and lead phosphate levels rise by up to 0.2% and are on par with or higher than those of the OPC control. Results demonstrated that the acceptable amount of lead oxide and lead phosphate in cement pastes is 0.2% wt. of the total cement content without affecting the mechanical properties of cement pastes. The initial and final setting times of cement pastes increase with increasing lead oxide and lead phosphate content. The concrete mixes containing 0.2% of lead oxide and lead phosphate enhances the attenuation properties for gamma rays and fast neutrons than the control mix. It has been observed that lead phosphates have dual effect on reinforced concrete represented in improving the compressive strength, besides, acting as anodic passivation supporting the passivation of steel reinforcement and suppressing the corrosion that could ensue due to penetrating aggressive ions.