Study On Effect And Properties Of Aluminate Cement And Wollastonite Modified Magnesium Phosphate Cement

Magnesium Phosphate Cement(MPC)is a good repair and reinforcement material,with fast setting and hardening,high early strength,good volume stability and good bonding performance with concrete.In this paper,aluminate cement and wollastonite were used to modify magnesium phosphate cement to form a composite system of magnesium phosphate cement.The mechanical properties,water resistance and corrosion resistance of the composite system were studied in order to obtain a modified magnesium phosphate cement with good performance.In this paper,the control variable method was firstly used to study the influence of water binder ratio,magnesium phosphorus ratio,retarder content and other factors on the compressive strength and setting time of magnesium phosphate cement net slurry,and to determine the basic mix ratio of magnesium phosphate cement net slurry.On this basis,the influence of different content of aluminate cement and wollastonite on setting time,mechanical properties,water resistance and corrosion resistance of magnesium phosphate cement was studied.X-ray diffraction analysis(XRD)and scanning electron microscopy(SEM)and other microscopic methods were used to analyze the hydration products and microstructure of magnesium phosphate cement composite system,and further study the improvement mechanism of aluminate cement and wollastonite modified magnesium phosphate cement.The results show that:(1)With the increase of retarder content,the setting time of magnesium phosphate cement paste increases and the compressive strength decreases.When the water-binder ratio increases from 0.14 to 0.20,the setting time of magnesium phosphate cement paste is prolonged,and the compressive strength of magnesium phosphate cement paste increases first and then decreases.When the water-binder ratio is 0.18,the compressive strength of magnesium phosphate cement paste is the highest.When the ratio of magnesium to phosphorus increases from 4/1 to 7/1,the setting time of the net magnesium phosphate cement paste decreases,and the compressive strength increases first and then decreases,and the compressive strength of the net magnesium phosphate cement paste is the highest when the ratio of magnesium to phosphorus is 6/1.(2)The reaction of magnesium phosphate cement composite system after adding water was dominated by the acid-base reaction of magnesium phosphate cement,and the addition of aluminate cement and wollastonite had little effect on the setting time of magnesium phosphate cement.The aluminate cement and wollastonite have filling effect,interaction effect and wrapping effect in the magnesium phosphate cement composite system,and the compressive strength of modified magnesium phosphate cement for 28 d in air curing and the compressive strength in water curing are improved.The addition of aluminate cement and wollastonite can improve the strength retention and water resistance of magnesium phosphate cement.(3)The main hydration product of magnesium phosphate cement paste is potassium struvite.When the p H value of solution is about 8.5,the solubility of potassium struvite reaches the minimum value.The p H value of acid and alkali solution can promote the dissolution of potassium struvite,so the corrosion resistance of magnesium phosphate cement paste is poor.The addition of aluminate cement and wollastonite can improve the corrosion resistance of magnesium phosphate cement,which is related to the filling effect,interaction and coating effect of aluminate cement and wollastonite in the magnesium phosphate cement composite system.