Physical Mechanics And Microscopic Characteristics Of Various Alkali-Activated Tungsten Slag Cementitious Materials

At present,tungsten slag are treated by storing in tailings ponds or backfill into mines.The amount of slags increased from 17.3 to 22.26 billion tons in China from 2015 to 2020.However,the comprehensive utilization rate of tailings is only about 30%.The slags not only occupy a lot of land and waste many available resources,but also pollute the environment.Therefore,improving the utlization rate of slags has become a hot research topic at domestic and overseas.In this paper,the mechanical characteristics of alkali-activated slags were studied by using unconfined compressive strength,the microscopic characteristics were studied by SEM,XRD and FTIR.The factors of alkali-activated materials properties including alkali type,curing age,alkali cintent,and curing temperature were considered.The main conclusions of this paper are as follows:（1）The four activators effectively excite tungsten slag.The unconfined compressive strengths of the tungsten slags treated with NaOH,Na₂SiO₃·9H₂O,and K₂SiO₃ solutions increase with the alkali content at 80℃,and is the strongest at 11%alkali content.The 1 day and the 3 days strength of the tungsten slags treated with KOH solution decrease with the alkali content;strengths after 3 days of curing first increase and then decrease with the alkali content;and is the strongest at 8%alkali content.The strengths treated with 11%alkali content first increase and then decrease with the curing age.Increasing the curing temperature is beneficial to reinforce the samples,but too high a curing temperature in the specimen lead to a partial reduction in strength within 80℃.（2）The morphology of gels change gradually with the increase of alkali content,curing temperature,and curing time.Specifically,the（C,N）-A-S-H gel forms in the specimens treated with NaOH change from the membrane,the flocculent to the I,II,and III type reticular.The II reticular gels form with the increasing temperature.The（C,K）-A-S-H gel forms in the samples treated with KOH change from the membrane and the flocculent to the I,III,and IV type reticular type.The IV mesh gels form at 60℃and 100℃.The irregular flaky produce at 100℃.The（C,N）-A-S-H gels forms in the specimens treated with Na₂SiO₃·9H₂O change from the film and the floccule to the glass,the powder,and the gel floccule.The powder gels form at 60℃and 100℃.The irregular flaky products produce at 100℃.The（C,K）-A-S-H gel formed by K₂SiO₃ activated slag mainly coexists in the form of film and powder.The IV reticulated and glassy gel gradually form with temperature,alkali content,and curing age.（3）The（C,N）-A-S-H and the（C,K）-A-S-H gels are generated in the samples excited by NaOH,Na₂SiO₃·9H₂O,KOH,and K₂SiO₃,respectively.The pirsonites are generated under the action of NaOH,which is independent of the curing temperature,and increase with the alkali content and curing age.The minerals such as K₂CO₃,KHCO₃,and K₂Ca（CO₃）₂ are produced in the samples treated with the KOH,increase with the alkali content,anddecrease with the curing temperature and the curing age.There is none new mineral in the samples activated by the Na₂SiO₃·9H₂O and K₂SiO₃.（4）The infrared spectrum results show that the alkali content,curing temperature,and curing age affect the degree of hydration reaction of alkali activated tungsten slags.The intensity of Si-O absorption peaks in the specimens activated with NaOH,KOH,and K₂SiO₃ decrease with the curing age and the temperature;However the absorption peak intensity in the specimens activated with Na₂SiO₃·9H₂O increase with the curing age and the temperature.（5）The NaOH is an optimal activator for the tungsten slags.The optimal curing time is 42 days,the optimal alkali content is 11%,and the optimal curing temperature is 80℃.The gels generating in the tungsten slags treated with the NaOH solution are dominated by the three-dimensional network.The strongest strength is 42.85 MPa in this research,meeting the requirements of M10 building bricks.This study provides scientific basis and technical reference for the utilization of tungsten slag resources and the production of unburned bricks.