Study On Performance And Application Of High Performance Concrete With Circulating Fluidized Bed Desulfurization Ashes

With the popularization of circulating fluidized bed(CFB)technology,the solid waste CFB desulfurization ashes are piled up in large quantities,which not only occupies a large amount of cultivated land but also causes great pollution to the environment.At present,the research on fly ash has been relatively mature,and relevant regulations have been issued.The use of fly ash for the preparation of high-performance concrete has also been promoted.However,there are few related studies on CFB desulfurization ashes and they have not been effectively utilized.CFB desulfurization ashes have their own volcanic ash activity and self-hardness,making it possible to be used in the building materials industry.Therefore,this paper proposes to use desulfurization ash and desulfurization slag to replace fly ash with the same proportion and then mix with silica fume to prepare high performance concrete.Study on the influence of the type and dosage of admixture on the mechanical properties and durability of high performance concrete,which provide a comparative study for fly ash,desulfurization ash and desulfurization slag.At the same time,the prepared high performance concrete is applied to the concrete filled steel tube(CFST)structure to explore the effect of high performance concrete in the CFST structure,and the influence of core concrete material on the performance of CFST is also studied.The research and results of this experiment are as follows:(1)In this experiment,10%,20%,30% fly ash,desulfurization ash or desulfurization slag were mixed with 9% silica fume to prepare high performance concrete,and the compressive strength was tested.The compressive strength of desulfurization ash and desulfurization slag high performance concrete are higher than that of fly ash high performance concrete,and the strength grade of all test pieces can reach C60 level.With the addition of fly ash and desulfurization slag test specimens,with the increase of the dosage,the compressive strength of the concrete is gradually reduced,and 10% of the test piece has the highest compressive strength;With the addition of desulfurization ash,the compressive strength of the concrete increases first and then decreases with the increase of the dosage,and the compressive strength is the largest when the dosage is 20%.(2)The anti-freeze performance of high-performance concrete specimens was studied.It was found that when the dosage of the concrete specimens with fly ash,desulfurization ash or desulfurization slag are gradually increased,the mass and strength loss rate of concrete will decrease first and then increase.When the dosage is 20%,the concrete has the best frost resistance performance.Under the same dosage,the mass and strength loss rate of desulfurization ash are the smallest.The desulfurization slag and desulfurization ash are not much different.The mass and strength loss rate of fly ash is obviously higher than that of desulfurization ash and desulfurization slag test piece.It can be seen that the desulfurization ash test piece has the best frost resistance performance.(3)The test conducted a study on the anti-carbonization performance of high-performance concrete specimens.It was found that when the dosage of the concrete specimens with fly ash,desulfurization ash or desulfurization slag are gradually increased,the carbonation depth of concrete increases gradually.With the extension of carbonation age,the carbonation depth of concrete increases gradually.Early growth is faster,and growth is slow in the later period.When the three admixtures are under low dosage,the carbonization depth of the test piece is low,and the test piece with the fly ash content of 10% and 20% has a carbonization depth of substantially zero.When the dosage of the three kinds of admixtures are 10% and 20%,the anti-carbonization performance: fly ash>desulfurization slag>desulfurization ash.When the dosage is 30%,the carbonization depth of the fly ash is less than the desulfurization slag in the early stage,and gradually surpasses the anti-carbonization in the later stage.The anti-carbonization performance: desulfurization slag > fly ash > desulfurization ash.(4)In this test,the prepared high-performance concrete is applied to the CFST structure,and the axial compression performance of the CFST is studied.It is found that the loading process of the concrete-filled steel tube can be divided into elastic stage,elastoplastic stage and plastic stage.The specimens are ductile failure and the failure type is shear-slip failure.With the gradual increase of the content of the three admixtures,the ultimate compressive bearing capacity of the CFST is gradually reduced.When the test piece enters the yield state,the ratio of the bearing capacity to the ultimate bearing capacity decreases gradually,and the peak displacement,peak strain and ultimate displacement at failure increase gradually,and the ductility of the test piece is better.When the content of the three admixtures is 10%,the ultimate bearing capacity: fly ash>desulfurization slag>desulfurization ash test piece,the desulfurization ash test piece has the best deformation ability;when the dosage is 30%,the ultimate bearing capacity: Desulfurization sulphur>Desulfurization ash>Fly ash,at this time,the deformability of the desulfurization ash specimen is still the best;when the ultimate bearing capacity of the specimen is not much different,the desulfurization ash specimen has better deformation ability,the fly ash test piece is poor.The measured values of the ultimate bearing capacity of CFST are similar to those of the unified theoretical model and the limit theory model.In addition to desulfurization ash,the ultimate bearing capacity of CFST is proportional to the compressive strength of standard concrete,that is,the higher the concrete strength,the greater the ultimate bearing capacity of CFST.