Modification Of Magnesium Oxysulfade Cement And Preparation And Application Of Foaming Materials

Magnesium oxysulfade cement has the advantages of lightweight,low alkalinity,good adhesion,non corrosion of steel bars,non hygroscopicity,rich raw materials,simple production process,and low production energy consumption.It has enormous application potential in the field of civil engineering materials and is currently receiving attention.However,due to the poor strength and durability of magnesium oxysulfade cement,as well as the problems of a single type of modifier and a long setting time after modification in the current modification technology,its promotion and application in practical engineering are limited.Therefore,it is of great significance to develop new modifiers for magnesium oxysulfade cement and study the application of modified magnesium oxysulfade cement.This article first explores the effects of new modifiers hydroxyethylidene p Hosp Honic acid and amino methylene p Hosp Honic acid on the p Hysical and mechanical properties,hydration products,water resistance,heat resistance,sulfate resistance,and other durability of magnesium oxysulfade cement.The modification mechanism of the modifier on magnesium oxysulfade cement was analyzed by combining X-ray diffraction,scanning electron microscopy,and pore size analysis tester;Then,the modified magnesium oxysulfade cement was further modified using mineral admixtures,and the effects of mineral admixtures on the p Hysical,mechanical,and durability properties of the modified magnesium oxysulfade cement were studied.Finally,a lightweight and high-strength cement foam material was prepared using modified magnesium oxysulfade cement,and its sound absorption and thermal conductivity were studied.Hydroxyethylene p Hosp Honic acid modifier can significantly improve the water resistance,heat resistance,and sulfate corrosion resistance of magnesium oxysulfade cement.Compared with magnesium oxysulfade cement without the modifier,its 28 day softening coefficient increases from 0.47 to 0.87;The sulfate resistance level has also been increased from less than 30 times to K60;The heat resistance performance is also significantly improved at 200℃and 500℃.The experimental results of modifying agents on the mechanical properties and durability of magnesium oxysulfade cement show that the variety and dosage of modifying agents have a significant impact on the strength of magnesium oxysulfade cement.Hydroxyethylene p Hosp Honic acid and amino methylene p Hosp Honic acid can significantly improve the compressive strength of magnesium oxysulfade cement at different ages.The strengthening mechanism of two modifiers on magnesium oxysulfade cement is due to the chelation effect of magnesium ions,which changes the hydration process of magnesium oxysulfade cement,thereby promoting the formation and development of the crystalline p Hase of 5Mg（OH）₂·Mg SO₄·7H₂O（abbreviated as5·1·7 p Hase）,and filling some pores.This not only enhances the interaction force between hydration products,but also improves the compactness of magnesium oxysulfade cement,thereby improving the strength and durability of modified magnesium oxysulfade cement.Adding four types of mineral admixtures can reduce the flowability of magnesium oxysulfade cement slurry and shorten the initial and final setting times of the cement.And as the amount of admixture increases,the fluidity decreases and the setting time shortens.At the same dosage,silica fume has the greatest impact on fluidity and setting time,followed by fly ash,mineral powder,and ground converter slag,respectively.The influence of different admixtures on the mechanical properties of magnesium oxysulfade cement varies.When fly ash and mineral powder are added externally,the compressive strength of modified magnesium oxysulfade cement can be improved by28 days.The optimal amount of fly ash is 10%of the mass of magnesium oxide,and the optimal amount of mineral powder is 20%.The addition of silica fume reduces the strength of modified magnesium oxysulfade cement,while the addition of finely ground converter slag has little effect on the strength of magnesium oxysulfade cement.The analysis of XRD and SEM results shows that the addition of admixtures changes the relative content between different hydrates without altering the p Hase composition of the hydration products.The modified magnesium oxysulfade cement with 20%silica fume has the best water resistance,while the modified magnesium oxysulfade cement with 20%mineral powder and 20%silica fume has the best heat resistance.The optimal composition and ratio for the comprehensive performance of modified magnesium oxysulfade cement foam material were determined through orthogonal experiments,and the effects of apparent density and pore structure on the sound absorption and thermal conductivity of magnesium oxysulfade cement foam material were explored.The results indicate that as the apparent density of magnesium oxysulfade cement foam material decreases,its porosity increases,its sound absorption coefficient increases,and its thermal conductivity decreases.When the apparent density is 351 kg/m³,the compressive strength of magnesium oxysulfade foam material at 28 days is 1.3 MPa,and its sound absorption coefficient is above 0.45 for sound waves at frequencies ranging from 200 to 4000 Hz.For sound waves at frequencies ranging from 2400 to 2600 Hz,the sound absorption coefficient increases to 0.80,indicating that the prepared foam cement has good sound absorption effect.In addition,its thermal conductivity was measured to be 0.104 W/（m·K）,and its insulation performance is also good.