By using the phase composition analysis,differential scanning calorimetry (DSC)/thermogravimetric (TG) and SEM,the phase composition,pyrolysis characteristics and microstructure changes of recycled gypsum and its mechanisms were studied to reveal the differences among recycled gypsum,natural gypsum and plaster of paris.The results showed that the phase composition,pyrolysis characteristics and microstructure of recycled gypsum had changed.CaSO4·1/2H2O in the R-P reduced approximately 3.5%,and the first and second dehydration temperature dropped 8 ℃ and 6 ℃,respectively.The recycled gypsum crystal became irregularity,had uneven distribution of grain,and the crystal cracks and porosity also increased.The analysis showed that the reduction of CaSO4·1/2H2O in R-P is due to the decrease of the content of CaSO4·1/2H2O and uneven particle size distribution in the RG.And the main reason of the great difference of pyrolysis characteristics between natural and recycled gypsum is that the crystallization water dehydration enthalpy decreases and the particle size reduces.
