| In recent years,energy efficient and ecologically friendly buildings have been important in the housing and construction sector.Gypsum,as an ancient and novel material in construction materials,is favored and recommended by researchers.Among them,desulfurized gypsum,as a by-product of flue gas desulfurization in thermal power plants,is a solid waste resource with great development and application value.On the one hand,it can not only improve the pollution problems brought about by industrial development,but on the other hand,it can realize the economical and rational utilization of solid waste resources.The chemical composition of desulfurized gypsum is basically the same as that of ordinary building gypsum,both of which are calcium sulfate dihydrate(Ca SO4·2H2O).Compared with other gypsum powders,the desulfurized gypsum powder has renewable,small particle size,stable composition,less harmful impurities and purity Advanced features.And it has many advantages,such as light weight,fire prevention,good thermal insulation performance,good seismic performance and so on.However,the common drawback of gypsum construction products is poor waterproof performance,easy to soften after absorbing water,which greatly limits its development and use.In this paper,the modified silicon oil paraffin composite emulsion is combined with nano-silica,ultra-fine fly ash and mineral powder to modify the desulfurized gypsum to improve its waterproof performance,and to conduct a preliminary discussion on its mechanism.The main research results are as follows:(1)The modified emulsified silicone oil paraffin emulsion is prepared by compound emulsification of dimethyl silicone oil and liquid paraffin.The modified emulsified silicone oil paraffin emulsion is mixed into the desulfurized gypsum in different amounts separately.Various properties have been significantly improved.When the modified silicone oil paraffin compound emulsion waterproofing agent content is 1%,the softening coefficient of desulfurized gypsum is increased by 60% to 0.89,and the water absorption rate continues to decrease with the increase of the content When the amount is 4%,it can be reduced to below 15%,which significantly improves the water resistance of desulfurized gypsum.(2)In the study of single-doped nano-silica to desulfurized gypsum,the particle size of nano-silica is very small,which effectively fills the crystal pores of desulfurized gypsum,reduces the porosity of desulfurized gypsum,and makes desulfurized gypsum more compact,Thereby improving the water resistance of desulfurized gypsum.The test results show that the nano-silica with the amount of 0.4% and the particle size of 50 nm has the highest softening coefficient of 0.92 after being mixed with the desulfurized gypsum,an increase of 84%.(3)Based on the addition of nano-silica,study the optimal blending of nano-silica with ultra-fine fly ash and ultra-fine ore powder,while improving water resistance,the mechanical strength is significantly enhanced The results showed that the softening coefficient of the nano-silica-desulfurized gypsum sample with 8% ultrafine ore powder reached 0.889,an increase of 76.6%,and the absolute flexural and compressive strengths could reach 3.66 MPa and 13.16 MPa,respectively.(4)The modified desulfurized gypsum compounded with modified silicone oil paraffin compound emulsion and nano-silica,ultra-fine fly ash and mineral powder was studied.The test results show that the best mixing ratio of organic-inorganic composite high-efficiency additive is: silicone oil paraffin The amount of compound emulsion is 1%,the amount of nano-silica with a particle size of 50 nm is 0.4%,the amount of ultrafine fly ash is 10%,the amount of ultra-fine mineral powder is 8%,and the softening coefficient is up to 0.892,and The mechanical strength has been significantly enhanced,while further improving the water resistance of desulfurized gypsum. |
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