Study On Modification Of Magnesium Oxysulfide Cement By Aluminate Cement/Ferroaluminate Cement

Magnesium oxysulfide cement has light weight,good flame retardant,short setting time,noise insulation,insulation and other excellent properties,but its poor water resistance,high temperature strength loss and other defects,so that its application field is limited by many,therefore,it is necessary to modify magnesium oxysulfide cement,improve its water resistance and high temperature resistance.This thesis first studied the effects of aluminate cement and ferroaluminate cement on the basic properties of magnesium oxysulfide cement on the basic properties of magnesium oxysulfide cement after 28 days of curing at normal temperature.The experimental results showed that when the dosage of aluminate cement was between 10 and 20wt.%,The compressive strength and flexural strength of magnesium oxysulfide cement can be greatly improved at the same time.When the content of aluminate cement is 20wt.%,the compressive strength and flexural strength of magnesium oxysulfide cement are the highest,reaching 89.75MPa and 24.9MPa respectively.When the content of ferric aluminate cement is 10wt.%,the maximum compressive strength and flexural strength of magnesium oxysulfide cement are73.35MPa and 19.05MPa.In order to study the effect of aluminate cement and ferroaluminate cement on the water resistance of magnesium oxysulfide cement,the magnesium oxysulfide cement samples mixed with two kinds of cement were cured at room temperature for28 days and then soaked in water for 7 days,14 days and 28 days.The experimental results showed that the strength retention coefficients reached 0.94,0.88 and 0.86when the aluminate cement content was 10 wt.%,and 0.93,0.93 and 0.92 when the ferroaluminate cement content was 10 wt.%,respectively,the water resistance of magnesium oxysulfide cement has been improved.The filling effect of AH₃gel,FH₃gel and M-S-H gel improves the water resistance of magnesium oxysulfide cement.This thesis also studied the influence of aluminate cement and ferroaluminate cement on the high temperature resistance of magnesium oxysulfide cement.The samples were calcined at 200℃,400℃,600℃and 800℃after 28 days of curing at normal temperature.The experimental results showed that the thermal insulation performance and volume stability of MOS were improved by adding two kinds of cement.The volume shrinkage of samples mixed with two kinds of cement at different temperatures was lower than that of blank samples,and the optimal use temperature of magnesium oxysulfide could reach 600℃.When calcined at 200℃,5·1·7 phase loses 5 crystalline water,the cement matrix shrinks,the apparent density increases,and the compressive strength increases;When calcined at 400℃,the 5·1·7phase will lose the remaining crystalline water to form 5Mg（OH）₂·Mg SO₄,and the compressive strength will decrease significantly.When the temperature is raised to600℃or above,the 5·1·7 phase and Mg（OH）₂will completely decompose and the mechanical properties of the sample will be lost.The experimental results show that when the content of aluminate cement is10～20wt.%,When the content of ferroaluminate cement is 10 wt.%,at the same time,it can improve the basic properties,water resistance and high temperature resistance of magnesium oxysulfide cement at room temperature.After adding two kinds of cement,the service temperature of magnesium oxysulfide cement can reach800℃.