Microstructure and micromechanical properties of magnesium phosphate cement

This paper presents a systematic study on the evolution of phase composition, microstructure and micromechanical properties of magnesium phosphate cement (MPC) and their relations to macroscopic mechanical properties. The results indicate that the microstructure of MPC is mainly composed of a crystal region of potassium magnesium phosphate hexahydrate (MKP) and a hybrid region of magnesium oxide and amorphous hydration products. The elastic modulus and hardness of MKP crystals are 20.18 GPa and 1.15 GPa, respectively. Amorphous hydration products may consist of MgKPO4 and Mg3 (PO4)2. The elastic modulus of amorphous MgKPO4 drops gradually from 51.4 GPa to 29.2 GPa with increasing curing age towards the elastic modulus of crystalline MKP, while the elastic moduli of amorphous Mg3(PO4)2 and unreacted MgO are approximately 160 GPa and 300 GPa, respectively. The macroscopic strength of MPC is mainly dependent on its pore structure rather than the micromechanical properties of hydration products.