Study On Preparation Of Crack Resistant Alkali-activated Slag Steel Structure Fireproof Coating

With the increase of fireproofing awareness of people,the steel structure fireproof coating is increasingly used in steel structures.For outdoor steel structure fireproof coating,the crack is easy to appeare,and the fireproof coating often falls down.when it is exposed in the external environment for a long time.The fireproof property and other properties of alkali-activated slag are better than that of ordinary portland cement.When the alkali-activated slag is used in steel structure fireproof coating,its properties can be improved.The alkali-activated slag steel structure fireproof coating(abbreviated to "JKS coating")with better mix proportion was determined by an orthogonal experiment.The cracking resistant behavior of JKS coating was mainly studied through a partly-restrained shrinkage ring test by adding polypropylene fiber in JKS coating.Based on this mix proportion of JKS coating,the anti-permeability performance of the JKS coating was optimized by an electric flux method by adding silylation powder in JKS coating.The bond strength and the fireproof property of JKS coating was optimized by changing activator type in JKS coating.Combined with pore structure,SEM and other macro test results,the micromechanism of JKS coating was revealed.The research results show that:1.Based on the preliminary mix proportion of JKS coating,changing the dosage of PVA,edispersible emulsion powder,expanded vermiculite and fire retardants(Mg(OH)2/Al(OH)3=0.32(mass ratio)),the property of JKS coating was studied,and the better mix proportion of JKS coating was obtained.When the dosage of PVA changes from 0 to 2.8%,the bond strength of JKS coating increases;when the dosage of redispersible emulsion powder changes from 3.8%to 6.6%,the bond strength of JKS coating slightly increases first and then decreases;when the dosage of expanded vermiculite changes from 13.4%to 19.4%,the fireproof property of JKS coating increases;when the dosage of fire retardants changes from 10.7%to 15.70%,the fireproof property of JKS coating increases first and then decreases.2.Based on the better mix proportion of JKS coating,with the increasing dosage of polypropylene fiber,the micro cracks of JKS coating decreases because of the bridging effect of fibers,so the cracking resistant ability of JKS coating becomes better.Based on the mix proportion of JKS coating with polypropylene fiber,the anti-permeability performance of JKS coating becomes better with the increase of silylation powder in the JKS coating.3.Based on the obtained mix proportion of the JKS coating with silylation powder and polypropylene fiber,by changing activator type,namely using sodium silicate,sodium sulfate(NS)or combined activator(namely 80%sodium silicate and 20%NS(mass ratio)),the bond strength and the fireproof property of the JKS coating were further studied.The bond strength and the fireproof property of the JKS coating with silylation powder,polypropylene fiber and the combined activator are the best because sodium silicate can provide SiO32-ions,which can accelerate polycondensation process and produce more gel.4.The bond strength and the fireproof property of the optimized JKS coating meet demands of national standard for steel structure fireproof coatings(GB14907-2002),and it has better cracking resistant behavior.Compared to commercial steel structure fireproof coatings,the comprehensive properties of the optimized JKS coating are better,and its cost is lower,Therefore,the optimized JKS coating has a good promotion and application prospect.