Abstract: The relationship between physical and chemical properties of limestone and the activity of lime was studied by rapid calcining the limestone at the temperature, which was much higher than the typical calcination temperature of active lime. The lime activity was tested by the titration of hydrochloric acid, and the phase compositions of limestone and lime were tested by XRD. The grain size of CaCO3 and the microstructure variation of CaO grains were analyzed by SEM. The results showed that the smaller CaCO3 grain size of the limestone resulted in better sintered situation of CaO and higher lime activity after calcining the limestone rapidly at high temperature. When prolonging the calcination time to 15min at 1450℃, the CaO grains in the lime that obtained by calcining the limestone with different CaCO3 grain size had fused and grown. The fusion and growth of CaO grains led to the significant decrease of the lime activity. The lime activity was greatly influenced by the content of SiO2 in the limestone. When the content of SiO2 was higher, the lime activity after calcining decreased remarkably. Therefore, the smaller CaCO3 grain size and the lower content of SiO2 of the limestone lead to the higher activity of lime after calcining the limestone rapidly at high temperature.

Key words: limestone, lime reactivity, high temperature, rapid calcinaion, grain size