Abstract: In the light of utilizing MSWI fly ash in cement－based materials, cementitious activity by means of specific compressive strength, the effect of chemical activators on cementitious activity of cement paste containing MSWI fly ash in the hydration of early ages and their effective mechanism of action were investigated and analyzed． Results show that MSWI fly ash has a low cementitious activity at early hydration, especially when the replacement was more than 20％． Therefore, in order to make sure pastes with MSWI fly ash have enough early strength, chemical activators CaSO4, KAl(SO4)2, Al2(SO4)3 and Na2SiO3 with a dosage ranging from 1％ to 3％ were used to activate the early cementitious activity of fly ash － cement paste, respectively． And, it shows that they all can significantly improve compressive strength of cement pastes containing MSWI fly ash, activating the early cementitious activity of the system inside． However, this effect decreased as the curing time prolonged．
