Study On Preparation And Properties Of Coal Gangue Based Polymer Solidified Soil

As one of the largest solid waste residues discharged in China ’s annual coal mining,coal gangue is piled up year by year due to its low utilization rate.The piled coal gangue not only wastes valuable land resources but also seriously threatens the regional ecological environment.Therefore,it is urgent to improve the comprehensive utilization of coal gangue.Geopolymer,also known as geopolymer,is a new type of inorganic aluminosilicate cementitious material with a three-dimensional network structure in space,which is stimulated by aluminosilicate raw materials in an alkaline environment.The structure of the material is similar to that of zeolite.It has the characteristics of high early strength,acid and alkali corrosion resistance and high temperature resistance.The main component of coal gangue is silicon aluminum mineral,which is an ideal raw material for geopolymer cementitious materials,Therefore,in this paper,coal gangue in Lingshou County,Shijiazhuang City,Hebei Province was used as raw material to prepare coal gangue-based polymers under the action of water glass solution as an alkaline activator and used to solidify soil.Through experimental test and theoretical analysis,taking the modulus,concentration and mixing ratio of alkali activator,mixing ratio of coal gangue,curing conditions and other factors as the influencing factors,the influence of different factors on the mechanical properties of solidified loess of coal gangue cementitious materials is explored,and the optimal mix ratio of solidified loess of coal gangue base polymer is studied.On the basis of the optimal mix ratio,the relevant mechanical properties of coal gangue cementitious material solidified loess were analyzed by mechanical test,and the curing mechanism was revealed by scanning electron microscope test and nuclear magnetic gap test.The main research contents are as follows:(1)Through the study of thermal activation of coal gangue mineral activity,it is found that the optimum temperature range of thermal activation of coal gangue in this area is 700～800℃.700℃ was selected as the thermal activation temperature of the early orthogonal test of coal gangue,and the orthogonal test of four factors and four levels L16(45)was designed.Considering the influence of different alkali activator modulus,incorporation ratio,concentration and coal gangue incorporation ratio,the optimum mix ratio of coal gangue base polymer cementitious material was determined:alkali activator modulus M=1.2,concentration 50%,incorporation ratio 27%,coal gangue incorporation ratio 54%.(2)On the basis of the optimal mix ratio,the mechanical properties of loess solidified by coal gangue cementitious materials with different thermal activation temperatures were studied by using coal gangue parts with different thermal activation temperatures,and the best thermal activation method of coal gangue was determined.According to the alkalinity of the alkali activator,the coal gangue of each thermal activation temperature was dissolved,and the leaching content of SiO2 and Al2O3 in the coal gangue was tested in this environment,and the active SiO2 and Al2O3 in the coal gangue were quantitatively analyzed.The results show that 700℃ and 750℃ are the best thermal activation temperature of the coal gangue.The leaching rates of SiO2 and Al2O3 from coal gangue calcined at 700℃ and 750℃ for 2h in 7mol/L NaOH solution were 8.66%and 8.83%,14.68%and 13.27%,respectively.(3)Through the dry-wet cycle,water stability test and freeze-thaw cycle durability test,the mechanical properties and quality changes of geopolymer solidified soil under the action of dry-wet alternation,long-term soaking water and freeze-thaw cycle were studied.Geopolymer solidified soil has low strength reduction rate and less water absorption after dry-wet cycle,and still has good integrity.Under long-term soaking conditions,the strength is further strengthened,the mass loss is low,no block collapse occurs,and the water stability is excellent.Although the quality is reduced after freeze-thaw cycles,the strength remains at a high level.(4)Through NMR test,it is found that with the increase of curing age,the total porosity of coal gangue base polymer solidified soil decreases continuously.The large pores inside the specimen gradually develop to the medium pores with the increase of age,while the small pores change in both directions of increasing and decreasing.The increase in the number of medium pores inside the specimen is the result of the combined action of the two processes of increasing small pores and decreasing large pores.