Study On The Preparation Of Magnesium-potassium Phosphate Cement Fireproof Coatings For Steel Structure

The steel structure building industry is in vigorous development period,but the poor fireproof performance and corrosion resistance of steel will cause huge loss,and block its development.Taking coating protection is the most effective and economical method to improve these properties of steel structure.This research firstly attempts to use MKPC for the preparation of fireproof coatings for steel structure according to the advantages of MKPC(excellent bonding properties,high temperature resistant performance,rapid hardening,early strength and corrosion resistance of steel in cement),make the coatings not only meet the requirements of relevant technical indexes,but also have certain corrosion resistance and environmental protection abilities.Based on the evaluation indexes of bond strength,fire resistance and dry density,comparative and orthogonal experiments were designed to determine the basic formula of coating.Then the performance optimization test was carried out to get the optimal performance of fireproof coating with its bond strength,fire resistance,compressive strength and dry density increased greatly.Finally the anti-corrosion property of steel in coating is studied,and a magnesium-potassium phosphate cement fireproof coating with excellent fireproof performance and corrosion resistance is obtained.By the SEM microstructure test,simultaneous thermal analysis test and pore structure analysis test,binder mechanism and refractory mechanism of coating are explained.The main conclusions are drawn as follows.1.Magnesium-potassium phosphate cement has a significant effect on the performance of the coating.With the decrease of P/M,the bond strength and fire resistance of the coating firstly increase and then drop.When P/M is 1/3,the amount of cement hydration products(MgKPO4.6H2O)is the most,the interfacial transition zone of cement paste and aggregate is most compact.And the cement hydration products will absorb heat and take off crystal water to retard the heating speed.Therefore the bond strength and fire resistance of the coating are the best.2.The additive agent can improve the performance of the coating.PVA can improve the bond strength and compressive strength of coating,but has an adverse effect on dry density.With the increase of zinc borate,as an environment friendly flame retardant,the fire resistance of coating firstly increases and then drops,but it has an adverse effect on bond strength.Silicon alkyl powder can improve the water resistance of coating.With the increase of the content of silicon alkyl powder,the bond strength of coating is decreased and the dry density is increased.3.MKPC has an effect on the corrosion resistance of steel in coating.Benefits from the good volume stability and bonding performance of MKPC,the coating obtains certain corrosion resistance ability.When P/M is 1/3,the coating has the best ability of corrosion resistance.4.Zinc phosphate as corrosion resistant filler,can significantly improve the corrosion resistance of steel in coating,but decrease the bond strength,fire resistance and compressive strength of coating.5.The prepared coating in this paper can meet the requirements of Fire Resistive Coating for Steel Structure(GB14907-2002).Compared with the commercially available fireproof coating,the formula of coating can not only get more excellent abilities of bond strength and fire resistance,shorten drying time to provide convenience for construction,but also defend the steel structure against the corrosion.