Synthesis And Hydration-resistance Technique Of High-quality MgO-CaO Clinkers And Its Application

The synthesis and hydration resistance techniques of high quality magnesia-calcia clinkers are studied in this paper. Furthermore, a kind of magnesia-calcia castable with excellent hydration resistance and application performances based on these techniques is developed.In the view of synthesis technique of high-quality magnesia-calcia clinkers, effects of mechanical activation two step calcining and hydration on the sintering of magnesia-calcia clinkers are researched on the basis of characteristics of raw material used in the experiments. Moreover, the sintering mechanisms of each process are also analyzed and discussed. In addition, experiments have studied and compared the action of different additives on sintering of magnesia-calcia clinkers. According to the results of experiments, a new production process of high quality magnesia-calcia clinkers is designed. The results of experiments show that magnesia-calcia clinkers can be sintered to high density at 1650 by this process and the density of samples can be up to 3.32g/cm3.In regard of hydration resistance technique of magnesia-calcia clinkers, the surface modification method by carbonating is studied. By forming a CaCO3 layer on the surface of magnesia-calcia clinkers treated by CO2, the hydration resistance of these clinkers can be improved effectively. The results show that the hydration resistance of treated samples is improved three or four times as much as that of untreated samples. However, it is found that the surface modification method by carbonating has itself disadvantages that reaction speed is relatively slow and treating time is too long. Therefore , the hydration and carbonation surface modification method is developed. In this method, mixed gas of vapor and CO2 is used and hopes to gain the end of speeding up the form of CaCO3 layer. The experimental results demonstrate that by using this method, the treating time can be reduced to the half and the hydration resistance of magnesia-calcia clinkers can be improved five or six times as much as untreated ones. In addition, the grain size and category have important influence on the effects of surface treatment method by hydrating and carbonating. The results of experiments show that with the decrease of grain size, the hydration resistance of treated samples is reduced. So it is necessary for little clinkers to increase the treating time. In the regard of effects of category of magnesia-calcia clinkers, these that have better microstructure can always have more excellent hydration resistance after treated by the method of the hydration and carbonation surface modification method.According to the results of our experiments, magnesia-calcia castable can be madesuccessfully from the magnesia-calcia clinkers treated by this method. At the same time, its hydration resistance, application performances and corrosion resistance are researched. The results show that this magnesia-calcia castable dried under the condition of 110 X 12h can be placed in the air for 3 months without any hydration phenomena. And its application performances and corrosion resistance are as good as and better than magnesia castable. So it can satisfy the requirements of industry practical application completely.