Study On The Effect Of Organic Waterproof Agent On The Performance Of Desulfurization Gypsum Block

Comprehensive utilization of a large number of desulfurization gypsum produced by thermal power plants can not only save resources but also protect the environment.At the same time,desulfurization gypsum block has the advantages of light weight,fire prevention,heat preservation and moisture preservation,which is widely used as building wall materials.However,the water resistance of desulfurization gypsum block is poor,and its strength is obviously reduced after immersion,which will cause serious frost phenomenon,affect the mechanical properties and appearance,and limit its application range.In view of this,this paper systematically studies the effects of adding sodium methylsilicate,dimethylsilicone oil and polymethylhydrosiloxane on the mechanical properties,waterproof properties and anti frost properties of desulfurization gypsum blocks,the effects of adding sodium methylsilicate and aluminum powder on the anti frost properties and mechanical properties of desulfurization gypsum blocks,and the mechanical properties and anti frost properties of desulfurization gypsum blocks mixed with organic waterproof agent.infrared spectrum(IR),scanning electron microscope(SEM)and electronic energy spectrum(EDS)were used to study the mechanism of organic waterproof agent on the performance improvement of desulfurization gypsum block.The main results are as follows:(1)In the range of 0.2wt.%～1.4wt.%,with the increase of the content,the strength of desulfurization gypsum block increases first and then decreases,the surface contact angle increases continuously,the water absorption rate decreases continuously,and the softening coefficient increases steadily;in the optimum content of 1.0wt.%,the strength of desulfurization gypsum block with the addition of MSA has little change compared with that without the addition,the water absorption rate decreases to 7%,and the softening coefficient reaches 0.85.(2)When the content of polymethylhydrosiloxane is in the range of 0.3wt.%～0.7wt.%,the strength of desulfurization gypsum block increases first and then decreases,the surface contact angle increases first and then decreases,and the water absorption decreases gradually.When the optimum content is 0.4wt.%,the performance of desulfurization gypsum block is significantly improved,the compressive strength is increased from 12.5MPa to 16.1MPa,and the flexural strength is increased from 4.9MPa At 6.8MPa,the water absorption decreased from 21.00% to 3.17%,and the contact angle changed from 0 ° to 121.75 °.(3)IR analysis shows that the hydrophobic film can be formed on the surface and pore wall of the block by adding sodium methylsilicate and polymethylhydrosiloxane,which is the main reason for the decrease of water absorption and the increase of softening coefficient of the block;SEM and EDS analysis show that the crystal morphology and microstructure of the dihydrate gypsum can be changed by adding sodium methylsilicate and polymethylhydrosiloxane,and the optimum amount of them can be obtained.The strength of block will not be reduced.(4)There is no synergistic effect between every two waterproofing agents(sodium methylsilicate,dimethylsilicone oil and polymethylhydrosiloxane),and the waterproof performance will be reduced.Compared with the optimum dosage of polymethylhydrosiloxane,the water absorption rate of desulfurization gypsum block is generally 15%,the surface contact angle is generally less than 50 °,the compressive strength is reduced from 16.5MPa to 12.0MPa,and the flexural strength is reduced from6.5MPa to 3.9Mpa.(5)The desulfurized gypsum block prepared by slurry molding process contains a lot of pores after molding and airing,and after adding drainage waterproof agent,the gypsum block will discharge 15wt%～20wt% of water after final setting,and the salt in the block will be discharged to prevent frost.(6)Under the condition of the best dosage,the order of improving the performance of desulfurization gypsum block by various waterproof agents is: 0.4wt.% content of polymethylhydrosiloxane > 1.0wt.% content of sodium methylsilicate > 0.15 wt.%content of sodium methylsilicate plus aluminum powder > dimethylsilicone oil > other water proofing agents.