| Because of the light weight, safety and convenient construction of the steel structure, the steel structure is the most common form in civil engineering. The steel itself cannot burn, but it has good thermal conductivity, which leads to the steel soften easily during heated, so as to lose the mechanical strength. The fire duration of the steel structure is poor. This shows that the fire protection of steel structure is very important, and the most common fire protection method is coating protection. Currently on the market what is widely used in thin and ultra-thin fire retardant coatings for steel structures, is mostly organic substrate what will release harmful gases in the case of fire, which is hazardous to human health. And it is sensitive in humidity, performance decaying fastly, and has a low fire resistance either, which is great harmful to people's health in the production and construction process. The inorganic non- expansive coating is based on the coating thickness to isolate the flame from the substrate, and to delay the speed of temperature transferring to the substrate, so as to improve the fire resistance rating of the substrate. This kind of coating is thick, with the big dosage, and the construction craft is complex. It is easily damaged and falling off, and difficult to apply in some of more complex steel structure and high-altitude construction. So the research of the composite steel structure fire retardant coating of environmental protection is the main directionThe NaOH and water glass are used as activators in this paper to stimulate metakaolin, which is made of a new cementitious material, called geopolymer as the base material of fireproof coatings, supplementing acrylic solution as auxiliary film-forming substances, using the composite expansion flame retardant system which is consisted by expandable graphite(EG), ammonium polyphosphate(APP), melamine(MEL) and pentaerythritol(PER), adding the fillers and additives, to develop a new type of thin coating compound waterborne expansive steel structure fireproof coating, inorganic and environmental friendly. Uniform test method is used to optimize the coating formulation and the performance of coatings is evaluated by simulated big panel combustion method. Then DSC-TG test methods were carried out to analysis the microstructure of the coating and the mechanism of fire retardant paint fire was explored. Through the result of this test, the factors influencing the properties of the coatings can be analyzed.It is shown that:(1) The base material with pure acrylic solution and polymer, intumescent flame retardant system using composite EG system and P-N-C system, the optimal ratio whose properties can meet the standard requirements is got, with thickness of 6.54 mm, and 87 min of fire resistance;(2)Dropping geoploymer can reduce the fire performance in a certain extent, it will decrease the bonding strength and charring layer strength of coating, and make the texture become loose and fall off easily, will also shorten the surface dry time. But when in firing, the coating has geoploymer produce less pungent smell than has not geoploymer;(3)When the binder is pure acrylic solution, and the flame retardant is expandable graphite, the fire duration is the highest, up to 158 min. At the same time, construction performance, expansion effect and charring layer status are the best;(4)The mass ratio between acrylic solution and geopolymer is less than 1, the charring laye r of coating formed by fire has loose texture, which is easy to fall off, so the resistance is poor, and refractory time is generally 30-40min; if the mass ratio between acrylic solution and geopolymer is more than 1 the charring layer is very hard, which is not easy to fall off by fire, so the refractory is a long time, more than 60 min, while both of them have good expansion effect. |
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