Abstract:

The effects of 45,105,165,500 ℃ heat-treated desulfurized gypsum on the properties of super sulfated cement were studied.The basic physical properties of the prepared super sulfated cement were characterized.Results showed that ce-ment with 45 ℃ and 500 ℃ heat treated desulfurized gypsum owned longer setting time,while the setting time of cement with higher water requirement of normal consistency had been shortened by 105 ℃ and 165 ℃ heat treated desulfurized gypsum.The workability of freshly mixed rubber sand was significantly reduced with the same water-binder ratio.Cement with 500 ℃ heat treated desulfurized gypsum had better mechanical properties than 45,105,165 ℃ heat treated gypsum.Micro analysis found that the main hydration products of super sulfated cement mixed with desulfurized gypsum after heat treatment at differ-ent temperatures were hydrated calcium silicate,ettringite and gypsum.A large amount of ettringite was produced in the later hydration stage of super sulfated cement with heat treated desulfurized gypsum after 500 ℃,while the ettringite mineral phase was less in the hydration products of cement with desulfurized gypsum heat treatment at 45,105,165 ℃.The desulfurized gypsum treated at 105 ℃ and 165 ℃ was easier to absorb the mixed water,which making mechanical properties lower for reducing the homogeneity of samples.

Key words: desulfurized gypsum, super sulfated cement, hydration products, microstructure