Analysis Of Hydration Characteristics And Mechanism Of Ground Fly Ash In Cement Concrete

Fly ash is a kind of active mineral resource,which is widely used in cement and concrete industry and is of great significance to protect the environment.Because the surface of fly ash is rough and the particle size is large,the performance of cement concrete prepared directly is low.Therefore,the effect of particle size and particle morphology on the hydration reaction of fly ash in cement concrete still needs to be studied by mechanical grinding.In this paper,the raw material of the power plant is used as the raw material,the grinding of the fly ash and its application in the cement-based material are studied.The hydration activity of the fly ash in the cement is analyzed by chemical reaction,and the mechanism and the change rule of the fineness and the content of the ground fly ash on improving the performance of the cement concrete are investigated by means of micro-analysis.The main research results are as follows:(1)The specific surface area and particle size morphology of the fine fly ash are analyzed by adjusting the grinding system of the grinding medium,grinding time and ball ratio.The results show that the mechanical grinding can effectively reduce the particle size of the fly ash.In order to improve the performance of fine fly ash.(2)The reaction degree of fly ash in slurry was measured by"hydrochloric acid titration",the hydration degree of cement mixed paste was measured by chemical binding water method,and the effect of fine fly ash on hydration activity of cement-based material was studied by means of micro-analysis of XRD and SEM.The higher the specific surface area,the higher the reaction degree of fine fly ash in cement hydration system.The hydration activity of ground fly ash doped with 806m~2/kg is the highest,which is 31%higher than that of raw fly ash.(3)The strength of cement mortar is measured by mixing different fineness and amount of ground fly ash into cement mortar.The early strength of cement mortar mixed with fly ash is lower than that of cement mortar,but the strength of cement mortar is improved obviously at the later stage of cement sand,and the strength of cement sand with different fineness and amount of fly ash is improved obviously in the later stage.The fineness of fly ash has a significant effect on the strength of cement mortar.The compressive strength of ground fly ash with 10%specific surface area of 803m~2/kg is 1.2 times higher than that of original fly ash.(4)The early compressive strength of fly ash mixed with concrete after grinding by a laboratory ball mill is obviously improved compared with that of raw ash sample at low admixture amount.The experimental results show that the early compressive strength of fly ash is much higher than that of raw fly ash.Due to the fine aggregate effect and activity effect of fly ash,the internal structure of fly ash is more dense,and the porosity is reduced effectively.The concrete prepared by grinding fly ash with 10%content can show good impermeability and carbonation resistance.