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中文摘要：
通过对煅烧菱镁矿尾渣与二级菱镁矿所得MgO膨胀剂（MEA）组成、微观结构、活性及膨胀特性的研究,探讨了低品位菱镁矿制备MEA的可行性。结果表明,菱镁矿尾渣中方解石、白云石及铁元素等杂质的存在使MEA中f-CaO含量较高,方镁石含量较低;菱镁矿尾渣MEA中MgO晶粒为条状颗粒,而非二级菱镁矿MEA的球粒状,晶粒尺寸变大,晶粒间排列紧密,MEA颗粒表面有裂纹存在;柠檬酸法检测低品位菱镁矿所制MEA活性时应调整柠檬酸用量;有效膨胀组分含量低的情况下,800℃煅烧掺量为4wt%、6wt%和8wt%及850℃煅烧掺量为8wt%时,掺菱镁矿尾渣MEA水泥浆体的膨胀率比掺二级菱镁矿MEA水泥浆体的膨胀率大。可见,在一定条件下低品位菱镁矿所制MEA膨胀性能较高品位菱镁矿所制MEA好,有利于低品位菱镁矿矿产资源的有效利用。
英文摘要：
Feasibility of producing MgO-type expansive agent（MEA）from low-grade magnesite was explored by investigating components,hydration activity,microstructures and expansion properties of MEA produced from magnesite tailings and grade 2magnesite by calcination.Results first show that：magnesite tailings have varieties of impurities i.e.calcite,dolomite,iron element,etc,leading magnesite tailings MEA to have lower content of f-MgO and higher content of f-CaO.Compared with independently spherulitic microstructure in grade 2magnesite MEA,the MgO grains in the magnesite tailings MEA are strip-shaped,the crystallite dimension is large and its arrangement is close,and cracks are easily generated on surface of MEA particles.Citric acid addition should be adjusted when the activity index of MEA produced from low-grade magnesite is tested using citric acid;Though magnesite tailings MEA have lower content of effective expansive agent,the expansion of cement paste in magnesite tailings MEA can be more than that in grade 2magnesite MEA when magnesite tailings MEA are calcined at 800℃ with 4wt%、6wt%and 8wt%calcinations agent added or 850℃and 8wt%added.Therefore,under certain conditions,expansion property of MEA from low-grade magnesite may be better than that from high-grade magnesite,which is conducive to the effective use of low-grade magnesite.
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