The effects of calcined phosphogypsum on the hydration process of the autoclaved silicate products were investigated in this paper.The influence of adding phosphogypsum calcined at different temperatures on the hydration rate of autoclaved silicate products was analyzed for un-reacted Ca(OH)2 content and combined water.The hydrates were determined with XRD and SEM.It was found that the hydration of autoclaved silicate products with added phosphogypsum calcined over 500℃ was greatly improved.The hydrates of the autoclaved silicate products with added phosphogypsum calcined over 500℃ had more un-reacted Ca(OH)2 content and combined water in the same curing time

and the research indicated that adding phosphogypsum calcined over 500℃ could also reinforce the compressive strength of autoclaved silicate products.It was pointed out that the aluminate phase present in the raw materials cannot hydrate to form more ettringite during autoclaved curing

and rapid formation of such hydrates as calcium silicate hydrate (1) and tobermorite with a more compact structure is the main reason for strengthening autoclaved silicate products.