Study On The Characteristics Of CFB Ash Slag And Its Application In The Preparation Of Concrete For Lightweight Partition Board

Circulating fluidized bed（CFB）combustion technology is an advanced clean coal-fired technology.With the increasing number of CFB boilers,a large number of CFB ash slag piles up.The CFB ash is collected from the flue,and the CFB slag is discharged from the bottom.There is a big difference between CFB ash slag and ordinary pulverized coal boiler ash slag,people also have limited understanding of CFB ash slag,which brings great difficulties to the utilization of CFB ash slag.In order to promote the utilization of CFB ash slag,this paper takes the CFB ash and slag of Datong thermal power plant of China coal as the research object.Based on the systematic study of the basic characteristics of CFB ash slag,the influence of CFB ash and CFB slag on the performance of cement mortar is discussed.The lightweight partition board of CFB ash and slag is reinforced by ceramsite and fiber.The main research contents and achievements are as follows:（1）The chemical composition,mineral composition,activity and water requirement of CFB ash were studied.The results show that CFB ash has high SO₃,Ca O content and high loss on ignition.The main mineral components are Ca O,C and II-Ca SO₄.The content of amorphous material is high.It has high pozzolanic activity and certain self hardening property,and has no poor stability.CFB ash has small fineness,loose structure and high water demand.The content of SO₃,Ca O and loss on ignition of CFB slag are lower than those of CFB ash,and the main mineral composition is quartz.The fineness modulus of CFB slag is small,which has the characteristics of more at both ends and less in the middle.The structure of CFB slag is loose and porous,and most of them are flaky structure,which has high water demand and high crushing value.（2）The influence of the amount of CFB ash and the excess substitution coefficient on the mechanical properties and expansion and shrinkage properties of cement-based CFB slag mortar is studied,which provides the basic preparation for its application in lightweight wallboard.The results show that CFB ash has high activity and good strength of cement mortar when used as admixture.When the standard sand is replaced by CFB slag as fine aggregate,the strength of mortar decreases by about 50%,but the strength increases greatly after the replacement of CFB ash.CFB ash can increase the expansion rate of cement mortar,while CFB slag can greatly increase the dry shrinkage of mortar.The addition of CFB ash can reduce the dry shrinkage of mortar.（3）By adding ceramsite to improve the strength and reduce the bulk density of CFB ash slag concrete,the mix proportion of concrete for lightweight partition board prepared with CFB ash slag is studied and optimized.The results show that with the increase of the excess substitution coefficient of CFB ash,the compressive strength of the concrete increases,especially the early strength increases significantly,the dry apparent density increases little,and the softening coefficient increases first and then decreases.With the increase of ceramsite content,the strength of CFB fly ash slag ceramsite concrete first increases and then decreases,the dry apparent density decreases significantly,and the weight loss is obvious.When the excess substitution coefficient is 2.1 and the volume ratio of CFB slag to ceramsite is 1,the comprehensive performance of the concrete is the best.The 28d compressive strength reaches 25.9MPa,which is 22.2%higher than the basic formula,and the softening coefficient is 97.9%,which meets the performance requirements of lightweight ceramsite concrete for partition board.（4）The effect of adding mode,length and amount of polypropylene fiber on strengthening and anti cracking of CFB ash slag ceramsite concrete for partition board was studied.The results show that the shorter the fiber is,the easier the dispersion is,and the longer the fiber is,the better the reinforcement effect is.When 19mm fiber with0.75kg/m³ is used,the strength of CFB slag ceramsite concrete is the best,the 28d compressive strength is 15.0%higher,and the 28d flexural strength is 19.6%higher.After adding polypropylene fiber into CFB ash slag ceramsite concrete,the number of cracks is not significantly improved,and the crack resistance grade is still L-1,but the total cracking area is greatly reduced,and the crack resistance performance is improved by more than 40%.