Study On Freeze Resistance Of CFB Slag/Gypsum High-strength Baking-free Bricks

Energy-saving and environment-friendly baking-free bricks have become a new type of building wall material promoted by China?which can replace clay sintered bricks?.In northern regions,the problem of poor freeze resistance of baking-free bricks is a key factor restricting the promotion and application of baking-free bricks.In view of the problem of poor freeze resistance of baking-free bricks,this paper studied the effect of ultra-fine ash and organosilicon water-repellent on CFB slag/gypsum high-strength baking-free bricks,and systematically investigated the ultra-fine ash content and organosilicon water-repellent.Influence of water dosage on freeze resistance of CFB slag/gypsum high-strength baking-free bricks.The main research object of this paper is CFB slag/gypsum high-strength baking-free bricks.The research content has the following aspects:?1?Study on the effect of molding system and maintenance system on the freeze resistance of CFB slag/gypsum high-strength baking-free bricks;?2?To study the effect of ultra-fine ash with different contents on the water absorption,apparent porosity,mass loss rate and strength loss rate of CFB slag/gypsum high-strength baking-free bricks after freezing and thawing;?3?To study the effect of different additives organosilicon water-repellent on the water absorption,apparent porosity,mass loss rate and strength loss rate of CFB slag/gypsum high-strength baking-free bricks after freezing and thawing;?4?Through XRD,SEM,DTA,IR analysis of ultra-fine ash or organosilicon water-repellent on the CFB slag/gypsum high-strength baking-free bricks freeze resistance impact mechanism.The paper analyzes the hydration process,microstructure and strength properties of CFB slag-desulfurized gypsum system and reveals the influence of ultra-fine ash and organosilicon water-repellent on the freeze resistance of CFB slag/gypsum high-strength baking-free bricks.The results show that:?1?The molding system and curing system play an important role in the apparent density of CFB slag/gypsum high-strength baking-free bricks.The molding pressure is26MPa,water-solid ratio 0.13,glue ratio 7/3,curing temperature 75?,and curing time9h.CFB slag/gypsum high-strength baking-free bricks have the best density and freeze resistance.?2?The addition of ultra-fine fly ash increases the content of CFB slag/gypsum high-strength baking-free bricks hydration products.When the ultra-fine fly ash content is 5%,the apparent density of CFB slag/gypsum high-strength baking-free bricks,The water absorption rate and apparent porosity were the best.After 15freeze-thaw cycle tests,the baking-free bricks had the lowest quality loss rate and strength loss rate and all met the standard requirements.?3?The main component of the organosilicon water-repellent is a silicon-oxygen bond?Si-O?as the main chain,and the remaining chain is an active group such as-OH,-CH₃,and-C₆H₅,which may interact with the surface active group or adsorbed water of the substrate.Condensation reactions,forming primary and valence bonds,hydrogen bonds,or attracting each other with dipoles,and strongly bonding with the surface of the substrate,allowing non-polar organic groups to align outwards,resulting in a strong hydrophobic network of silicon oxygenated molecular membranes give CFB slag/gypsum high-strength baking-free bricks a hydrophobic effect as a whole.When the content of organosilicon water-repellent is 1%,the water absorption and freeze resistance of CFB slag/gypsum high-strength baking-free bricks are the best.