Based on the preparation principle of cementitious materials of dehydrated hydrate phases two expansive agents for concrete,D_0 and D_1,were prepared from industrial wastes including fly ash and phosphogypsum.The main component of D_0 and D_1 are C_3AH_6 dehydrated hydrate phases and AFm dehydrated hydrate phases respectively.Expansion performance of the expansive agents was tested.The results show that both of the expansive agents can meet the limited expansion rate in water required for the expansive agen...