Study On The Influence Of Fiber/Expanded Perlite On Desulfurization Gypsum Properties

In the process of thermal power generation,a large amount of industrial solid waste desulfurization gypsum will be produced.If it is not properly treated,the accumulation of desulfurization gypsum will occupy a large amount of land resources and pollute the environment.Therefore,the utilization of desulfurization gypsum has become a major social problem that people must face.At present,the most potential application field of desulfurization gypsum is construction materials,especially wall materials,but its own low strength,poor water resistance and other problems restrict its promotion and application.At the same time,in order to realize the light desulfurization gypsum,lightweight materials are added.But because of the floating phenomenon of lightweight materials,in view of the problems of light material floating,low strength and poor water resistance after desulfurization gypsum molding,this paper studied and prepared a kind of light,high strength and water resistance desulfurization gypsum composite material.The main research contents and conclusions are as follows:1.The expanded perlite was added into the desulfurization gypsum,and the single factor test method was used to optimize the preparation process of the desulfurization gypsum to solve the floating problem of the expanded perlite.The research shows that the desulfurization gypsum and citric acid are mixed and stirred evenly,and then 2.0%encapsulated expanded perlite is added,and the encapsulation ratio is expanded perlite:desulfurization gypsum:water=1:3:1.8,and finally water is added to prepare desulfurization gypsum specimens by direct molding.The up-floating phenomenon of expanded perlite is obviously improved,and its absolute dry flexural strength,saturated water flexural strength,absolute dry compressive strength and saturated water compressive strength are 4.09MPa,2.18MPa,10.08MPa and5.67MPa,respectively.The dry apparent density is 1.182g/cm~3.2.To further optimize the distribution form of light material in the desulfurized gypsum and improve the mechanical properties of the composite,through orthogonal test,the preparation process of fiber/expanded perlite/desulfurized gypsum composite was improved by taking fiber incorporation method,slurry stirring method and vibrating times of the specimen as three factors.The results show that the optimal preparation process is as follows:first,the desulfurization gypsum is mixed with citric acid and stirred evenly,and then 2.0%encapsulated expanded perlite is added,and the encapsulation ratio is expanded perlite:desulfurization gypsum:water=1:3:1.8,and finally add the mixture of pre-stirred fiber and water,stir it evenly,and vibrate for 20 times to form.At this time,the floating phenomenon of expanded perlite basically disappears.The absolute dry flexural strength,saturated water flexural strength,absolute dry compressive strength and saturated water compressive strength of the composite are 4.66MPa,2.66MPa,11.23MPa and 6.51MPa,respectively.Compared with the fiber/expanded perlite/desulfurized gypsum composite prepared by the method of expanded perlite/desulfurized gypsum composite,they increased by 15.06%,10.37%,12.30%and 10.15%,respectively,and the dry apparent density is1.154g/cm~3,which decreased by 2.29%.3.The strength of desulfurization gypsum composites can be further improved by using different types of fibers with different dosage,single mixing and compound mixing,supplemented by admixtures(hydroxypropyl methyl cellulose HPMC).The results show that the optimal ratio of fiber mixing is no HPMC but mixed with three kinds of fibers,the content of which is 1.5%,and the proportion of three kinds of fibers is:0.3%polypropylene fiber fixed content,lignocellulose fiber:glass fiber=1:2.At this time,the composite material has the best performance.The absolute dry flexural strength,saturated water flexural strength,absolute dry compressive strength,saturated water compressive strength and dry apparent density are 7.14MPa,3.21MPa,21.26MPa,8.71MPa and 1.187g/cm~3,respectively.Compared with no fiber doped,they increased by 46.01%,21.13%,52.95%,27.90%and 2.15%.4.The water-proofing agent can improve the impermeability of the material and reduce the water absorption rate.The water resistance of fiber/expanded perlite/desulfurized gypsum composite can be improved by single or double mixing of silicone water-proofing agent and paraffin emulsion.The research shows that the optimal ratio after adding waterproofing agent is adding 2.0%paraffin emulsion alone..At this time,the overall performance of the composite material is excellent.Compared with the non-mixed water repellent agent,the full water bending strength is 3.38MPa,which increased by 3.05%,the dry apparent density is 1.188g/cm~3,which decreased by 0.75%,the water absorption rate of 2h and 24h are7.99%and 10.16%,respectively,which decreased by 42.56%and 29.00%.The bending softening coefficient and compression softening coefficient are 0.630 and 0.601,respectively,which increased by40.94%and 56.10%.