Development of Magnesium Phosphate Cement Based on Low-Grade MgO.

Area of Science:

• Materials Science
• Inorganic Chemistry
• Sustainable Construction Materials

Background:

• Magnesium phosphate cements (MPCs) are advanced inorganic materials with applications in radioactive waste confinement.
• Traditional MPCs utilize high-purity dead-burnt magnesia (DBM), which is energy-intensive to produce.
• Low-grade magnesia, a waste by-product, presents an opportunity for cost reduction and enhanced sustainability.

Purpose of the Study:

• To investigate the feasibility of using low-grade magnesia (≈58% MgO) in the production of magnesium potassium phosphate cements (MKPCs).
• To evaluate the impact of the magnesium-to-phosphate (M/P) molar ratio and relative humidity (RH) on cement properties.
• To assess the potential of these eco-friendly cements for radioactive waste immobilization.

Main Methods:

• Preparation of MKPCs using low-grade magnesia and a phosphate source.
• Characterization of mechanical properties (compressive strength), microstructural development, and mineralogical composition.
• Systematic variation of M/P ratios and curing conditions, including relative humidity, over a one-year period.

Main Results:

• Low-grade MgO is confirmed as a viable precursor for MKPC production.
• The presence of minor phases in low-grade MgO does not impede the formation of K-struvite (KMgPO₄·6H₂O).
• Cement development is significantly influenced by M/P ratio and RH; an M/P ratio of 3 yielded optimal results.

Conclusions:

• MKPCs produced from low-grade magnesia offer a cost-effective and sustainable alternative to conventional cements.
• Cements with an M/P ratio of 3 exhibit desirable compressive strength, low porosity, and mineralogical stability.
• These properties make the developed MKPCs promising candidates for radioactive waste confinement applications.