Study On Strength Characteristics Of The Fly Ash Stabilized By Cement

In recent years,with the society paying more attentions to the problem of fly ash,the comprehensive utilization ratio of fly ash is increasing continually,and has led to great social,economic and environmental benefit.But there are still a mass of abandoned fly ash.In coastal area,fly ash is often discharged with seawater;such is the same in Qingdao and Dalian.Wet fly ash from sea contains salt,which makes it sharply different from common fly ash.Currently speaking,there are difficulties in using wet fly ash from sea,and it can't be used in the production process of building materials and wall materials,but it can be used in the reclamation and road laying. On the other hand,a great deal of wet fly ash from sea has been stacked in the open air,and has formed a large area of fly ash foundation.How to utilize the fly ash foundation is an urgent problem.The quality of the stacked wet fly ash is not steady. It is low in shear strength and high in liquefaction potential with the function of static force and vibration.So the fly ash foundation must be stabilized when it is used as building foundation.Through laboratory tests,the purpose of this subject is studying on strength characteristics of the fly ash stabilized by cement,and supply fundamental theoretical direction for foundation treatment especially fly ash foundation treatment. Firstly,the dry fly ash was mixed by the seawater and tap water respectively in order to simulate the wet fly ash.Unconfined compression tests and analysis by Scanning Electron Microscope(SEM) and X-Ray Diffration(XRD) were conducted under the different age,different sorts of cement and cement content,and get the strength value of unconfined compression and corresponding stress-strain curve.And then the stabilizing effect was contrasted and its mechanism was analyzed with the microscopic test.Secondly,a certain amount of fly ash was soaked in seawater with different conditions.The effect of soak on the fundamental properties of fly ash was analyzed initially.The laboratory test indicated that the strength of stabilized fly ash was increased with the increase of age whether in the seawater or tap water condition, and the increasing range is larger in the early stage,decreased in the later stage,and the stabilized fly ash has well durability.But the dissoluble salt in seawater influence the increase of late strength and the increased rate is diminish evidently compared with tap water.The strength of stabilized fly ash was increased with the increase of cement content,and the increasing range is larger in the later stage.The slag cement can lower the influence of seawater on the strength of stabilized fly ash,and is more applicable in salt-rich foundation treatment compared with the Portland cement.On the age of one day,the plastic property of the stabilized fly ash with low cement content is larger,and its plastic property decreases,and its brittle property raised as the increase of age and cement content.The fly ash after soaked compared with the dry fly ash,its grain are not smooth,eroded by the seawater,its specific gravity of grain increased,and its coefficient of curvature after particle size analysis.The strength of cylindrical sample increase with the extension of soaked time,but it is lower compared with the stabilized fly ash.