Abstract：The effect of sulphoaluminate cement on the performance of Portland cement was studied．The early strength of Portland-based composite cement is increased by the addition of proper amount of sulphoaluminate cement and gypsum．Th e setting time of studied cement is reduced as the amount of additive increased．By means of XRD and other measurements，the mechanism of perform ance modification of this composite cement was studied．The AFt and aluminate gel form ed during hydation，mainly cause the strerIgh increasing and setting time
reducing．
Key words：composite Portland cement；sulphoaluminate cement clinker；perform ance；mechanism