Study On The Fabrication And Properties Of Magnesium Oxychloride Cementious Composites

In addition to cement, gypsum, lime, sodium silicate, magnesium oxychloride cement (MOC cement) is another important component of inorganic cementitious material. At present the hydration mechanism, forming technology and other aspects of MOC cement is in-depth study, but there are still not solving some important puzzles just like poor water resistance, deformation rate is high and absorbing moisture in high humidity atmospheres of magnesium cement-based composite materials in the practical application process.The influence on the property of MOC materials was studied with setting some modifiers added singly or together with other admixtures simultaneously in this paper.Using various of modifiers such as phosphoric acid, iron alum, latex, acrylic ester, silica powders, fly ash, coupling agent and the polypropylene fiber to improve the property of the MOC-sawdust material and MOC-EPS particles material. Compare with the specimen added singly, the modifiers that have fine modification effect are double-doped and multi-doped in the experiment to get the comprehensive property of composite material. The main conclusions were draw as following.1.As the basic proportion of modified MOC cement was the molar ratio of MgO/MgCl2=7, single-doped 1% phosphate by weight could significantly improve the MOC-sawdust composite materials' water resistance, but reduce the mechanical properties of materials. Single-doped 4% iron alum by weight could effectively increase early strength and the dissolution rate of chloride ion was inhibited, the phenomenon of bittern accumulation hadn't happened on the sample.2. The strength of MOC-sawdust composites can be greatly improved by blending with fly ash and iron alum. The best multi-doped formulation was that the proportion of phosphate, iron alum and fly ash were respectively 1%,4%,20%. The water resistance could be kcn=0.9 and the deformation rate just only 0.5%o after the deformation was stabile.3.The flexure strength of MOC-EPS particles material can get the maximum by the basic proportion of modified MOC cement was the molar ratio of MgO/MgCl2/H2O=7/1/13, the mix proportions of coupling agent, polypropylene fiber were respectively 0.6%,0.6%. The water resistance of MOC-EPS particles material by single-doped phosphate or iron alum is worse than double-doped of them. The water-absorbing capacity is low and the water resistance is excellent when the phosphate is combined with iron alum. The water resistance could be kcn=1.01.4. The swelling of MOC-EPS particles material is increasing with the increase of curing time. Fly ash combined with phosphate and iron alum can greatly improve the deformation. The deformation rate just only 0.562%o after the deformation was stabile. The best multi-doped formulation was that the proportions of coupling agent, polypropylene fiber, phosphate, iron alum and silica powders or fly ash were respectively 0.6%,0.6%,1%,3%,10%,20%.