Study On The Application Of Circulating Fluidized Bed Ash Grouting Filling Material

With the rapid development of Chinese economy,exploiting of coal resources for many years has left a large number of goaf.In order to prevent surface subsidence and ensure no safety hazards for surface buildings,goaf filling is needed.Close to coal base,power plants are usually equipped with the combustion technology as Circulating Fluidized Bed boiler.Generally,CFB ash generated after combustion should be stacked or buried,occupying the land and causing serious impact on the ecological environment.In this paper,CFB ash was used to prepare low cost grouting filling material to fill goaf as the main raw material.The optimal mixture ratio of the grouting filling materials was obtained by testing and analyzing the working performance of the slurry,physical and expansive performance of the concretion,and analyzing the microstructure of the concretion by SEM and XRD.The result shows that:1.The prepared CFB fly ash grouting filling material,under the same initial fluidity,the fluidity and compressive strength of CFB fly ash grouting slurry are better than that of fly ash grouting slurry,and its expansion can compensate for the shrinkage of concretion;The working performance of slurry is little influenced,the compressive strength and expansion rate of concretion are great influenced by the quality of CFB fly ash.The compressive strength and expansion rate of concretion are certain influenced by the working environment of slurry;The ratio of CFB fly ash grouting slurry（CFBFA1）is cement content of 15%,CFB fly ash content of 85%,and water solid ratio of 1:1.2.The initial fluidity of slurry is 223mm,the compressive strength of concretion of 7d and 28d are 1.9MPa and 2.3MPa respectively,and the expansion rate of concretion of 90d is 0.006%,with micro-expansion property.It meets the technical requirements of goaf filling.2.The prepared CFB ash grouting filling material,under the same initial fluidity,the CFB ash grouting slurry has poorer fluidity,higher compressive strength and higher expansion rate than the fly ash and mechanism sand grouting slurry;The working performance of slurry is little influenced,the compressive strength and expansion rate of concretion are great influenced by the quality of CFB cinder.The compressive strength and expansion rate of concretion are certain influenced by the working environment of slurry;The ratio of CFB ash grouting slurry（CFBFA1,CFBC1）is cement content of 15%,CFB ash content of 85%,CFB ash ratio of 30:70and water solid ratio of 1:2.4.The initial fluidity of slurry is 223mm,the compressive strength of concretion of 7d and 28d are 8.8MPa and 10.8MPa respectively,and the expansion rate of concretion of 90d is 0.172%.It meets the technical requirements of goaf filling.3.The high content of CaO and SO₃ in CFB ash promote the formation of AFt in the hydration products of concretion of CFB fly ash grouting slurry and CFB ash grouting slurry.AFt fills the interspace of structure,improving the compressive strength.AFt is also a major factor in the formation of expansion of concretion.