Early hydration kinetics research of nano-SiO2 and cement composite cementitious materials
The effects of nano-SiO2(NS)on the initial and final setting time,compressive strength,flexural strength and hy-dration heat of NS cement composite cementitious system were studied by partial replacement of cement with nano NS.The hydration characteristics of NS cement composite cementitious system were analyzed by hydration heat,and the hydration reaction mechanism of NS cement composite cementitious system was analyzed based on Krstulović-Dabić Hydration kinet-ics model.The results showed that after replacement of cement with nano NS,the initial and final setting time of cement was advanced,the compressive strength of cement mortar at different ages was improved,but the fluidity of cement mortar was reduced.NS promoted the reaction rate of the hydration reaction of NS cement composite cementitious system in the early in-duction period,induction period,acceleration period and deceleration period,and the third exothermic peak appeared in the deceleration period,which made the acceleration period and deceleration period end ahead of schedule.NS significantly improved the reaction degree of crystal nucleation and crystal growth(NG),phase boundary reaction(I)and diffusion stage(D),reduced the proportion of stage I in the whole hydration process,speeded up the transformation from stage I to stage D,reduced the porosity and permeability in the slurry,increased the hydration resistance and advanced the stability period.
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