| Fly ash and desulfurization gypsum are the two major wastes of coal-fired power plants,and most of the waste fly ash and desulfurization gypsum from power plants are dumped into ash dumps and piled up into mountains.The current balance of fly ash piles is still huge,causing waste of land resources,soil salinization,and also contamination of groundwater;at the same time,the production of desulfurization gypsum is also growing year by year,which not only wastes land resources and causes a decline in air quality,but also poses a potential risk of heavy metal seepage.However,waste is a misplaced resource.Because of the volcanic ash characteristics of fly ash,we can use it as a cementing material,and the use of FGD gypsum on fly ash sulfate excitation,the two comprehensive use of artificial stone preparation,which not only conforms to the National Development and Reform Commission and other departments "on the 14 th Five-Year" guidance on the comprehensive utilization of bulk solid waste "platform,but also Reduce the amount of natural stone mining,and promote the scale of industrial solid waste high-value utilization.In this paper,fly ash and desulfurization gypsum were used as raw materials to prepare artificial stone by press molding method,and SEM,XRD and FT-IR were used to characterize the artificial stone specimens and clarify the mechanism of the influence of each component on the strength of the specimens.The main studies are as follows.(1)Firstly,the effects of three process parameters,namely raw material ratio,molding pressure and mixing method,on the compressive strength of artificial stone test blocks were studied.The results showed that the test block strength was greatly affected by the molding pressure,and the best raw material ratio of fly ash to FGD gypsum was 6:4when the water addition was 32%,the suitable molding pressure was 50 MPa,and the better mixing method was vibration stirring.(2)Secondly,the effects of the addition of three alkali excipients,namely calcium oxide,calcium hydroxide and sodium hydroxide,on the compressive strength of the artificial stone test blocks were studied,and the results showed that the strength of the test blocks was most affected by the amount of calcium oxide,followed by the amount of calcium hydroxide and least affected by the amount of sodium hydroxide.When calcium oxide is used as excitation agent,the amount of calcium oxide should be controlled at about 15%;when calcium hydroxide is used as excitation agent,the higher the amount of calcium hydroxide,the better the strength of the test block,but for cost reasons,it is recommended that the amount of calcium hydroxide be controlled at about 20%;when sodium hydroxide is used as excitation agent,the amount of sodium hydroxide that has the greatest effect on the strength of the test block is 15%.The best strength excitation effect among the three excitants was mixed with 15% calcium oxide,and the 28 d compressive strength of the test block was 59.33 MPa,but it should be noted that the final vertical expansion value of the test block was 0.70 mm.(3)Finally,the effects of the addition of three kinds of aggregate,namely standard sand fine sand,intermediate sand and gangue,on the compressive strength of the artificial stone specimens were studied,the results show that the standard sand fine sand and intermediate sand as aggregate,the best dose is 10%;0-2.5 mm gangue as aggregate,the best dose is 5%;when gangue dose is 10%,the larger the size of the gangue aggregate,the higher the compressive strength of the test block.The strength of the test block was affected by the aggregate admixture,the aggregate strength,the size of aggregate,the interface between the aggregate and the test block bonding problems.The best effect of the three aggregates on strength enhancement is mixed with 10% intermediate sand,and the 28 d compressive strength of test block is 71.30 MPa. |
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