Abstract: From the kinetic and thermodynamic point of view, the feasibility of phosphogypsum(PG) decomposition making cementitious material at low temperature was studied.The decomposition kinetics of PG with 10%-15% activated carbon(AC) were investigated at 1100-1250 ℃.The results show that the apparent activation energy of PG decomposition system is 299.88-382.85 kJ·mol-1, the pre-exponential factor is 18.64-25.61 s-1 and the most possible decomposition mechanism is Z-L-T function.The synthesis reaction of CaO and SiO2 was processing along with the decomposition during the calcination was confirmed by the thermodynamic calculation and microstructural analysis.According to the phase diagram of CaO-SiO2-CaSO4 system, adding some appropriate silicon aluminum modified components and adjusting the scope of raw material proportion have the potentiality to improve the compressive strength of cementitious material made from PG.

Key words: phosphogypsum(PG);CaSO4;activated carbon(AC);decomposition kinetics;thermodynamic calculation;cementitious material