复合型镁质胶凝材料的水化相及其硬化体显微结构

Hydration Phase and Microscopic Characteristics of Composite Magnesium Oxychloride Cement

将菱苦土与苛性白云石按一定比例混合构成复合型镁质胶凝材料,将其与氯化镁水溶液按n(MgO)/n(MgCl2)=5拌和后形成氯氧镁水泥硬化体,研究了该复合型镁质胶凝材料的水化相及其硬化体显微结构。该硬化体的强度随着菱苦土在苛性白云石中含量的增加,其不同养护时间的抗折和抗压强度均随之增加,24 h的最高抗折强度为9.07 MPa,28 d的最高抗压强度为183.50 MPa,说明将复合型镁质胶凝材料与氯化镁溶液拌和后,形成了具有一定强度的水泥石或氯氧镁水泥硬化体。XRD和IR测试结果证明形成的硬化体为5型相结晶体,其显微特征主要是大量的凝胶体形貌而非针(棒)状结晶结构,呈放射状的针(棒)状晶体仅在孔洞中存在。认为凝胶体是复合型镁质胶凝材料硬化体具有很高强度的来源。

In X-ray powder diffraction analysis and infrared absorption spectrum analysis,when composite magnesia cementitious material made up of caustic dolomite and calcined magnesite according to suitable proportion between the caustic dolomite and the calcined magnesite and mixed with aqueous solution of MgCl2 according to the 5 mole ratio of MgO to MgCl2,the hydration phase of the hardened composite magnesium oxychloride cement is Mg3（OH）5Cl·4H2O.The strength of the hardened composite magnesium oxychloride cement will increase when the percentage of the calcined magnesite added to the caustic dolomite.Its curing 24 h bending strength reaches 9.07 MPa and curing 28 d compressive strength up to 183.50 MPa.Thus the hardened composite magnesium oxychloride cement is formed.Its microscopic characteristics possess morphology of the main large gel phase,but not needle-bar-like crystals.The needle-bar-like crystals only exist in the holes.The main large gel phase is considered to be the source of very high mechanical strength of the composite magnesium oxychloride cement.