The Modification Research Of Foamed Magnesium Oxychloride Cement And The Effect Of Composite Surfactant System On The Performance Of Foamed Magnesium Oxychloride Cement

Magnesium oxychloride cementing material is a new type of rigid gelled material which adding different additive in magnesium oxychloride cement to enhance,modify,foam.There has many excellent properties,such as,hardening speed,high mechanical strength,strong bonding ability,good wear resistance,sound insulation,heat insulation,bittern corrosion resistance.The thesis study on the hardening of forming mechanism of magnesium oxychloride cement materials and develops a new type of lightweight magnesium oxychloride cement composites.With specific strength,foam expansion,foam half-life as the main index,studied the effect of n?MgO?:n?MgCl₂?,the specific gravity of MgCl₂ solution,different type and amount of foaming agent and stabilizing agent,foam volume on specific strength of foamed MOC and analyzed the phase composition and crystal structure by XRD and SEM.The results show that the optimum n?MgO?:n?MgCl₂?was 7⁸,the optimum specific gravity of MgCl₂ solution was 1.22¹.23.When n?MgO?:n?MgCl₂?:n?H₂O?=7:1:16,the specific strength was 4.46 n·m/kg.The foaming ability of 0.5%LAS solution was the best,foam expansion was 30.When m?TX-10?:m?LAS?was 0.5,the stable foam ability of solution was best,the foam half-life was 74 min at40?.The foam volume should be controlled in 200 ml to 600 ml every hectogram of MgO,the density of the foamed MOC was from 0.65 g/cm³ to 0.28 g/cm³.The hardening mechanism and preparation technology have been studied thoroughly through increasing stirring rate and prolonging mixing time at constant ratio of raw materials.This study described the effects of mixing procedure on properties of MOC,such as apparent viscosity,setting time,compressive strength,specific strength,phase composition and crystallographic structure which be by measured by using XRD and SEM.The results indicated that increasing stirring rate and prolonging mixing time changed apparent viscosity distinctly,shorten setting time,enhance mechanical property.Magnesium oxychloride cement stirring at 280rpm achieved the optimal mechanical performance after mixing 20 min.The apparent viscosity was 3.98 Pa·s,the setting time was 285 min,the compressive strength of Rigid MOC was 107 Mpa,the specific strength of Foam MOC was 4.22 N·m/kg.The effects of increasing stirring rate on the phase composition of magnesium oxychloride cement superior to prolonging mixing time.Increasing the stirring rate and prolonging mixing time which increase the dispersion state and accelerate the neutralization promote the strength of MOC by forming stable 5·1·8 phase,excellent needle-like crystals and continuous crystalline structure in the whole cement space.The technological properties of magnesium oxychloride cement which be stirred at 280rpm are better than 140 rpm.With specific strength,flexural Strength,softening coefficient as the main index,studied the effect of the types and amount of fillers and modifiers on mechanical properties and water resistance of foamed MOC.The results show that the fly ash and silica fume enhance specific strength and flexural strength significantly,the polypropylene fiber enhance specific strength and flexural strength simultaneously.The optimum adding amount of fly ash was 20%,the adding amount of silica fume should be controlled within 10%because of the phenomena of defoaming,the optimum adding amount of polypropylene fiber was 1%.The modification effect and mechanism of phosphoric acid and phosphate are all the same,the optimum adding amount as follows:phosphate 1%,potassium dihydrogen phosphate 1%,ammonium dihydrogen phosphate 0.5%,the modification effect of phosphoric acid is best.Ferrous sulfate could improve water resistance,but there is no contribution to mechanical properties,the optimum adding amount was 1.5%.The orthogonal experiment indicated that the optimal matching scheme of water resistant performance is fly ash:polypropylene fiber:phosphate=40%:1%:1%,the optimal matching scheme of mechanical properties is fly ash:polypropylene fiber:phosphate=30%:2%:1%.