氯氧镁水泥流变特性研究

Research on rheological properties of magnesium oxychloride cement

针对氯氧镁水泥早强快硬特性导致其制备的混凝土存在长距离运输时不易搅拌、难泵送等施工受限问题。通过旋转黏度试验测定了氯氧镁水泥浆体在不同剪切速率下的剪切应力及塑性黏度值,采用幂律(Power-law)流体模型拟合氯氧镁水泥流变曲线,并通过该模型分析氯氧镁水泥材料组成设计参数MgO、MgCl_2、H_2O的物质的量比对氯氧镁水泥浆体的剪切应力、塑性黏度及流变特性的影响。研究结果表明:Power-law模型适用于氯氧镁水泥浆体流变曲线拟合,其拟合判定系数均大于0.9,拟合度高,并且可以对稠度系数、流变指数等流变参数进行较好的描述;氯氧镁水泥浆体的剪切应力随剪切速率的增大而增大,而塑性黏度随剪切速率的增大先迅速降低后趋于平稳;剪切速率相同时,氯氧镁水泥浆体的剪切应力随MgO与MgCl_2物质的量比增大而增大,随H_2O与MgCl_2物质的量比增大而减小;随着水泥水化的进行,浆体剪切应力和塑性黏度均增大,当MgO、MgCl_2与H_2O的物质的量比为7∶1∶15时浆体最稳定。

The early hard and fast characteristics of magnesium oxychloride cement lead to the construction problems of the concrete with long-distance transportation, is difficult to stir and difficult to pump and so on, which limits the popularization and application of magnesium oxychloride cement material. The shear stress and plastic viscosity of magnesium oxychloride cement paste at different shear rates were measured by the rotational viscosity test. The Power- law model was used to fit the theological curves of magnesium oxychloride cement, and the influence of the design parameters on the rheological properties of magnesium oxychloride cement were analyzed by the model. The results show that the Power-law model can be used to fit the rheological curves of magnesium cement slurry, and the rheological parameters such as consistency coefficient and rheological index can be described. The shear stress of magnesium oxychloride cement paste increases with the increase of shear rate. The plastic viscosity decreasesrapidly and then tends to be stable. When the shear rate is the same, the shear stress increases with the increase of the amount-of-substance ratio of MgO to MgCl2, and decreases with the increase of the amount-of-substance ratio of H2O and MgCl2. With the hydration of cement, the shear stress and plastic viscosity increase. When the amount-of-substance ratio of MgO, MgCl2 and H20 is 7 ： 1 ： 15, the paste is the most stable. 7 tabs, 5 figs, 16 refs.