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In connection with the problems of fly ash used for cement and concrete admixture, the modification of different types of fly ash was studied in this paper..Firstly,the effect of heat treatment temperature,single dry grinding process,wet grinding process,composites process on stability of high calcium fly ash was studied. The results shown that mechanical grinding was the most basic method,combining with other modification methods such as adding water grinding,adding chemical admixtures（carbide slag,lime） grinding,the qualified products of high calcium fly ash could be produced.Secondly,for improving the high calcium ash’s early strength and increasing content in cement,the single dry and wet grinding process,dry and wet grinding with cement process,grinding with additive process were studied.Through the analysis of experimental results,all the process studied in this paper could be used to improve the early strength and the content of high calcium in cement,especially the early strength could be improved effectively by the grinding with cement process and adding the lime and Na2SO4 wet process.The final tests of this issue were to improve the early strength of cement added with low calcium fly ash.Based on wet grinding process,combining with chemical additives such as lime,sodium sulfate,and further process such as hydrothermal treatment of low calcium fly ash,the 3d strength of cement added with low calcium fly ash was improved significantly.
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