Experimental Study On The Properties Of Cement-maize Straw Ash Based Backfill Materials

Filling mining is an important part of green mining of coal mine,but the filling cost become the main bottleneck restricting filling technology popularization,reduce the cost of coal mine filling materials to promote coal mine filling mining plays a key role.In recent years,biomass power generation technology has been promoted in China,and the treatment of biomass ash has become an important content to be considered in the daily operation of biomass power plants,the study found that the biomass ash with volcanic activity,and after the cement hydration products of Ca(OH)₂ ash reaction to generate gelatum,increasing the later strength of cement base material.Choose maize straw ash as the research object in this paper,maize straw ash partly replace cement and fly ash is added to the coal mine cemented filling materials,first by particle size analyzer,x-ray photoelectron spectroscopy(XPS)analysis,scanning electron microscope(SEM),x-ray diffraction(XRD),electrical conductivity and zeta potential analysis the particle size distribution,chemical structure,microscopic morphology,mineral composition and ash activity of the maize straw ash and poplar leaves ash.Then the flow performance,compressive strength,dry shrinkage performance and AE response characteristics of uniaxial compression failure were studied by replacing cement and fly ash in cemented filling material using maize straw ash.The main conclusions are as follows:(1)It was found that the maize stalk ash prepared in the laboratory had pozzolanic activity,and the best activity was to burn it at 700?for 3 hours.Poplar leaf ash has low chemical activity and low zeta potential,so it is not suitable to partially replace cement.(2)When the cement was replaced by maize straw ash,the slump and expansion of cement-filled slurry tended to decrease first and then increase with the increase of the substitution rate.The slump expansion of filling slurry is minimized when the substitution rate is 10%.When the substitution rate is 20%,30%and 40%,the slump expansion degree of filling slurry is higher than the control group,which can promote the flow performance.When the fly ash was replaced by maize straw ash,the slump and expansion of cement-filled slurry showed a trend of increasing first and then decreasing with the increase of the substitution rate.When the substitution rate is 10%,the slump expansion degree of filling slurry reaches the maximum,and the flow performance is better than that of the reference group.When the replacement rate is 20%,30%and 40%,the slump expansion degree of the filling slurry is lower than the reference group and the flow performance is not strong.(3)The stress-strain curve of cement-maize straw ash based backfill materials can be divided into four stages:compaction stage,linear elastic stage,nonlinear elastic stage and failure stage.When the maize straw ash partially replaces the cement,the compressive strength of the cemented filling material is the maximum when the substitution rate is 20%at the 28-day age.It is also found from the microstructure that the structure of the product under this substitution rate is denser than other substitution rates,which promotes the growth of the compressive strength of the cemented filling material.The results of dry shrinkage test show that the dry shrinkage of cemented filling material is the largest when the replacement rate of maize straw ash is 20%.When the maize straw ash part replaces the fly ash,the maximum compressive strength of the cemented filling material is 40%,and the dry shrinkage of the cementing filling material under this substitution rate is the maximum.(4)When maize stalk ash partially replaces cement,the ringing count and energy are in the rising phase of the rising phase of the stress-strain curve of the cemented filling material.When the peak load is reached,the ringing count and energy reach the maximum.During the declining phase of the stress-strain curve,the ring count and energy are in a quiet period and an active period.When maize stalk ash partially replaces fly ash,in the compaction phase of the stress-strain curve,the ring count and energy are in the rising period,and the internal pores of the specimen are compacted;in the linear elastic phase,as the loading continues,Ringing count and energy are constantly increasing;in the nonlinear elastic phase,when the peak load is reached,the ringing count and energy reach the maximum;in the failure phase,the ringing count and energy change range is relatively stable initially,inside the test piece crack development,as the loading continues,the ring count and energy are active again,the internal crack of the specimen develops into a crack,and the overall failure of the specimen occurs.