Hydration Kinetics of Cement-based Materials With P_2O_5 Incorporated

By means of SEM,XRD and calorimeter C-80Ⅱ,the hydration characteristics and hydration kinetics of cement-based materials with and without P2O5 incorporated were investigated.It is found that the amount and size of hydration products incorporated with P2O5 were decreased dramatically.When 3.5% P2O5 was added in cement,total amount of hydration heat was decreased by 32.6% and initial and final setting were delayed by 1.10 h and 12.54 h respectively.In terms of mechanism analysis,P2O5 had little impact on cement hydration mechanism,and accelerating stage was controlled by chemical reaction,decreasing stage controlled by both chemical and diffusion reaction while stabilizing stage controlled by diffusion alone.The hydration resistance in both accelerating and decreasing stage was elevated while decreased in stabilizing stage.The activation energy in both accelerating and decreasing stage were reduced and increased in stabilizing stage.P2O5 was favorable to hydration of C3A yet retarded hydration of C3S and C2S.