Mechanical and hydration characteristics of cement with high content calcined coal gangue
The mechanical and hydration properties of"calcined coal gangue-cement clinker-gypsum"binder system are studied.The results show that the cementitious materials prepared by partially replacing the clinker with calcined coal gangue have better mechanical properties,and the optimal replacement amount is 35%.The strength of 7-day and 28-day can reach 23.8MPa and 29MPa.The incorporation of anhydrous sodium sulfate significantly improves the early strength and late strength of the above binder system,especially when the anhydrous sodium sulfate content is 5%.The strength of 3-day,7-day and 28-day can be increased by 100%,32.4%and 40%,respectively.The phase composition of cementitious materials before and after modification is analyzed by XRD and SEM.It is found that the incorporation of anhydrous sodium sulfate generates a large amount of Ca(OH)2 throughout C-S-H gel in the early stage of the system,and the presence of Ca(OH)2 accelerates the dissolution of gypsum and the formation of AFt,fills the pores,makes the structure of the system compact,and improves the early strength.
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