Study On Mechanical Properties And Action Mechanism Of Rice Husk Ash Cemented Backfill Based On Pozzolanic Effect

Agricultural production activities produce a large amount of cheap and easily available rice husks every year,and rice husk ash obtained by burning rice husks,as a biomass pozzolan material,has a very high content of amorphous silica.It is used as a cement admixture in cementbased building materials,and is less used in underground mine filling slurry.The backfill is an important factor for the safe mining of underground mines.Adding rice husk ash as a cement admixture to the backfill can not only ensure the mechanical properties of the backfill,but also save a lot of backfill costs for the mine,so it has broad application prospects and research.value.In this study,through a large number of literature review and a series of indoor experimental design and performance tests,the results show that rice husk ash can effectively enhance the relevant mechanical properties of the filling body when it is mixed with the filling slurry as a cement admixture,and its mechanical properties inside the filling body can be effectively enhanced.The pozzolanic reaction is the main factor to improve the long-term strength of the backfill.At the same time,the rice husk ash can fix part of the heavy metal ions in the backfill,thereby improving the subterranean environment around the backfill.The research content of this paper mainly includes the following parts:(1)Using the lime-sand ratio,slurry concentration and the addition amount of rice husk ash as variables,the effect of rice husk ash material on the anti-pressure properties of the backfill was studied.The research results show that: under the conditions of high lime-sand ratio and high slurry concentration,the increase of the content of rice husk ash can effectively enhance the compressive strength and strain characteristics of the backfill,which is different from the cement-bonded backfill.Compared with the lime-sand ratio,the slurry concentration has a greater impact on the strength of the rice husk ash filling with higher rice husk ash content.At the same time,the strain generated by the filling body in the compression test was analyzed,and the hydrated calcium silicate gel formed by the reaction between rice husk ash and internal substances during the development stage of the filling body was found through the macroscopic damage morphology judgment and the microscopic scanning electron microscope analysis.It will fill up a large number of pores generated by water absorption in the early stage,which will reduce the porosity of the filling body,reduce the amount of strain generated by compression,and gradually turn the filling body to brittleness.(2)Determine the activity of rice husk ash as biomass pozzolan by testing and calculating the pozzolanic activity index and pozzolanic strength contribution rate of rice husk ash under different ratios,and then select the ratio with the highest pozzolanic activity to carry out the same particle size quartz The sand replacement ratio test was carried out to trace the source of the effect of rice husk ash on the strength of the backfill.The research results show that: under the conditions of high lime sand ratio(1:4)and high slurry concentration(74%),high content of rice husk Ash(20%)has a larger volcanic ash activity index and volcanic ash intensity contribution,101.63% and 29.82%,respectively.At the same time,the contribution of rice husk ash to the early strength of the filling body comes from the filling effect,but for the long-term strength,the strength contribution provided by the pozzolanic reaction is greater and much greater than that provided by the filling effect.Therefore,for the rice husk ash material itself In other words,in order to further improve its influence on the strength of the filling body,it is necessary to process the material preparation process so that the content of non-qualified silica contained in the rice husk ash is increased.(3)The solidification effect of different dosages of rice husk ash on heavy metal ions at high lime-sand ratio and high slurry concentration was studied by TCLP toxicity leaching test,and the water quality of the leaching solution of four dosages of rice husk ash filling was evaluated in combination with groundwater quality indicators.The results show that the water quality of the four types of leachate is in line with the water quality standard of grade V of groundwater,and the filling of rice husk ash will cause great pollution to the hydrological environment around the filling area.At the same time,the rice husk ash material has strong adsorption and fixation for sulfur,chromium and boron elements,but has certain adsorption properties for manganese and arsenic elements,but when the content of rice husk ash increases,its adsorption capacity will be completely reduced.It shows a certain repulsion effect for phosphorus and barium elements due to the promotion of cement hydration reaction by rice husk ash.Here are 63 pictures,33 tables and 72 references.