Abstract: In this paper, the effects of different intumescent flame retardants on the properties of steel under fire were studied.Waterbased expansive coatings were synthesized with silica fume (SF) as binder and eggshell (CES) as filler.The effects of binder and filler on coating properties and fire resistance were studied by thermogravimetric analysis (TGA), scanning electron microscope (SEM), small gas burner test and furnace test.TGA results show that adding SF alone or combining with CES in SEM images can improve the residual weight and thermal stability of coatings, and improve the surface structure of coatings.The combination of SF, CES and flame retardant additives has the best fire performance, with the highest thermal stability, the largest expansion degree and the densiest surface structure, and has enough adhesion in the process of fire exposure.

Key words: expansion of coating, fireproofing, construction of steel structure, SEM