Basic Composition Design And Performance Test Of MAPC Based Fire Retardant Coatings For Steel Structures

Magnesium ammonium phosphate cement（MAPC）is a new type of cementing material,which has the advantages of fast hardness,early strength,high temperature resistance,good corrosion resistance and good bonding performance.In this paper,a fire retardant coating using magnesium ammonium phosphate cement（MAPC）as the base binder was developed,and its base mix ratio was designed and modified according to its fire resistance.Using compressive strength,fire resistance and water absorption as macroscopic characterization parameters,the micromorphology and phase composition were analyzed by XRD,TG and SEM-EDS.In this paper,the light aggregate was modified first,and the optimal modification solution and modification ratio were determined under the condition of ensuring the lowest water absorption.Then the light weight aggregate was added to MAPC based coating,and the optimal content of light weight aggregate was determined by parallel test.After adjusting the bone glue ratio and the fineness of white corundum sand,one of the coarse aggregates,the optimal bone glue ratio and the fineness of white corundum sand were determined by parallel test.Then add polypropylene fiber,basalt fiber,through the fire performance and strength test,determine the added fiber.Then,metakaolin,fly ash and Thioaluminate cement were added into MAPC based coatings,and the variety and dosage of mineral admixtures were determined by fire resistance and strength tests.Finally,Ti O₂ and aluminum tripolyphosphates were added to further modify MAPC based coatings.After determining the best modified formula of MAPC based coatings,the comparison test with existing Japanese SKK fireproof coatings was carried out,and the conclusion and prospect were made.The main test results are as follows:（1）By the modification of expanded perlite（EP）by ydjsyyj silane,the silanol group hydrolyzed by silane hydrolysis forms a film with Si O₂ on the surface of EP,which greatly reduces the water absorption rate of EP material,and its dilution ratio is 0.1.The modified EP material has a more positive effect on the fire performance of the MAPC coating than that of the unmodified EP material,and after adding the EP material,the fire resistance of the coating is increased due to the EP material having better fire resistance and heat insulation.However,the incorporation amount should not be too large,and it is best when the incorporation amount is 22.5%.（2）The bone-to-rubber ratio decreases,so that the fire resistance of MAPC coating first increases and then decreases.The reduction of aggregate increases the hydration substances between the aggregate particles,increases the crack resistance of the MAPC coating during combustion,and enhances the fire resistance of the specimen.However,with the further reduction of the bone-to-rubber ratio,the thermal insulation effect of the aggregate weakens,the thermal stability of the specimen deteriorates,and the specimen is more prone to cracking when burning at high temperature,resulting in its weakening of fire resistance,so it is appropriate to take the bone-to-rubber ratio of 0.3.（3）White corundum sand has the characteristics of high strength and high compactness,and the fineness of white corundum sand decreases,so that the fire resistance of MAPC coating first increases and then decreases.The fineness of white corundum sand is reduced,so that the surface of the coating becomes flatter when it is formed,the heating is more uniform,and the fire resistance is improved,when the white corundum sand is fine for an hour,the specific surface area of the white corundum sand is too fine,and the wetting water required increases,resulting in the water-cement ratio of the freshly mixed paint slurry increases,the connecting capillaries increase after the slurry hardens,and the thermal insulation performance of the hardened body becomes worse,and the mesh number of white corundum sand is 24.（4）The addition of external admixtures can improve the performance of MAPC coatings.The addition of basalt fiber and polypropylene fiber increases the toughness of the coating hardened body,delays the cracking and peeling of the specimen under the action of thermal stress,and strengthens the high temperature resistance,among which,the strength of the basalt fiber itself is higher,and the crack resistance in the high temperature state is more excellent,and the dosage is 5%.The incorporation of filler improves the granular gradation of solid powder in MAPC,achieves the purpose of refining the pore size,makes the open hole become a closed hole,reduces the heat propagation speed,and effectively improves the compressive resistance,flexural strength and fire resistance of the coating,among which 10%of the content of metakaolin is appropriate.On this basis,the incorporation of 1%Ti O₂ accelerates the hydration rate of MAPC cement,makes the coating denser,and further strengthens its fire resistance.（5）After comparative test,too long heating time makes the surface of MAPC coating cracks,resulting in the reduction of its fire resistance,when the basalt fiber content is increased,the heating resistance time is extended,compared with MAPC coating,SKK coating itself light and deformation resistance,has good ductility,when burned to 300°C,SKK coating can still be well adsorbed on the surface of steel,in the later stage of combustion,SKK coating fire resistance is better than MAPC-based coating fire resistance.Fig.66 Table 14 Reference 55...