Structural Design And Fire Performance Evaluation Of MKPC Based Fire Retardant Coatings For Steel Structures

As a new type of green material,steel structure has a broad development prospect,but steel structure is easy to soften under high temperature.Coating fire retardant coating on steel structure surface is one of the most efficient and economical fire protection measures.Potassium magnesium phosphate cement(MKPC)is a new type of green inorganic cementitious material,which has the advantages of fast setting speed,high early strength,good durability,high temperature resistance and good adhesion with various base materials,In order to make full use of the advantages of MKPC,the non expansive fire retardant coating for steel structure was studied with potassium magnesium phosphate cement(MKPC)as binder.In this paper,fluidity,compressive strength,tensile bond strength,fire resistance,hydration heat,water absorption rate as characterization parameters were tested.On the basis of determining the benchmark mix ratio,the forward tensile bond strength,fire resistance and cracking resistance of MKPC coating were optimized by adding additives.In view of the high water absorption of expanded perlite,it was modified,The modified expanded perlite not only reduces the water absorption,but also increases its strength,avoiding the phenomenon of easy breakage in transportation.The microstructure and phase composition of MKPC were analyzed by XRD,TG and SEM-EDS.The main results are as follows:1.The addition of white corundum sand can increase the consistency of MKPC paste,thus increasing the compressive strength of MKPC;the addition of metakaolin can improve the fluidity of MKPC mortar,and improve the compressive strength and fire resistance of the coating;when the content of TiO2 is 0.5%,the tensile bond strength of the coating is the highest;when the content of TiO2 is 1%,the fire resistance of the specimen is the best.At this time,the positive tensile bond strength of the coating decreases,but it still meets the requirements of "fire retardant coatings for steel structures"(GB14907-2018).2.In view of the high water absorption of expanded perlite,the lightweight aggregate was modified.The modified solution of expanded perlite is composed of silane impregnation solution and water at the ratio of 1:5.The water absorption rate of modified perlite is only 22%in 0.5h.The microstructure of expanded perlite is analyzed by SEM,and it is found that it can effectively block the contact between water and the pores in the expanded perlite.Through the test,it is determined that the content of modified expanded perlite instead of corundum sand is 20%.It can be seen that with the increase of lightweight aggregate,the fire resistance first increases and then decreases,which has a negative impact on the normal tensile bond strength of the coating,but can reduce the dry density and cost of the coating.3.The additive can improve the performance of MKPC coating.The addition of redispersible latex powder can greatly improve the forward tensile bond strength of the coating.When the content is 1%,the forward tensile bond strength increases by 36.9%,and when the content is 0.75%,its fire resistance is the best.The addition of glass fiber and polypropylene fiber can absorb heat when heated,avoid heat concentration,and improve the crack resistance of the coating.Figure 75 table 25 reference 93...