| As a chemical bonded material, Magnesium phosphate cement(MPC) can set and harden at room temperature. It has both characteristics such as stiff, high strength, high temperature resistance of ceramic material and the characteristics as good plasticity, adaptability, durability of cement materials. MPC has been widely used as rapid repair materials, disposal of nuclear waste application field and also have potential application in shielding radiation of large nuclear facilities for many advantages, such as fast setting rapid hardening, high early strength, good liquidity, high bond strength with the old concrete, low shrinkage and sintering free. As an efficient and clean energy, Nuclear energy has been widely used in power generation, medical and food sterilization application.There are certain risks especially for some individual man-made and nature disasters which will cause serious harm to human beings and the environment. So,it is necessary and particularly important to enhance the security of nuclear material and facilities to prevent radioactive material leakage at the early time.Based on this point, in this paper, a system research on γ rays rapid shielding material has been proposed. For fast setting and rapid hardening characteristics,MPC was selected to mix with barite and lead powder. Research in this paper focus on effect of barite and lead powder content on setting time, fludity,compressive strength and shielding performance of magnesium phosphate rapid shielding material. Secondly, By means of XRD and SEM analysis, thermal analysis, heat of hydration, pore structure analyzed studies on the thermodynamics of phase composition, microstructure and properties. Finally,adaptability, adhesion strength, expansion, extraction and the durability of barite-lead co-doping magnesium phosphate rapid shielding materials was studied preliminary.Through this thesis research, a new radiation protection material with good shielding performance and long-term stability is to be obtained.The results show that barite partly replace dead burned magnesia can significantly lower magnesium phosphate shielding materials quickly hydration,fluidity decrease, setting time extended, compressive strength increase and then decrease by increasing barite dosage.Compressive strength is highest when the dosage of barite is 30%, dosage of barite reached 50%, the compressive strengthof 1d up to 39.4MPa. After doping lead powder, with the increasing lead content,fluidity increases compressive strength show a downward trend generally, 1d compressive strength is 27.0MPa when mixing 20% lead powder.From the point of shielding effect, gamma rays shielding rate of magnesium phosphate cement rapid shielding materials increases with increasing dosage of barite. Sheilding rate is 57.7% when the dosage of barite is 50%. Barite-lead co-doping magnesium phosphate rapid shielding materials have a good effect on gamma ray. With the increase lead, liquidity and gamma-ray shielding efficiency increases, doping 20% lead, shielding efficiency can reach 70%.Magnesium phosphate cement rapid shielding material have a good liquidity,strong environmental suitability, high bonding strength with old concrete, good long-term strength development, low leaching of lead, good chemical stability and strong resistance to freezing and thawing. The MPC rapid shielding materials in thesis setting time ≤30min, the initial flow of ≥230mm, 1d compressive strength ≥30MPa, 1h adhesive strength ≥3MPa, magnesium phosphate cement rapid shielding material material has excellent radiation shielding properties and can be used as a quick repair materials, which is suitable for fast processing of nuclear emergency. |
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