| Fly ash is one of the largest coal fired by-products in China,and it is one of the industrial waste residue with the highest utilization level and the highest utilization level.It is not only beneficial to environmental protection but also to improve the added value of fly ash,and to some extent it is of great significance to breakthrough the limitation of comprehensive utilization of fly ash.The substitute material of fly ash as cement,which has become the most energy consuming building material after removing aluminum and steel,is widely used in cement industry and concrete engineering.It can effectively delay the hydration of cement,reduce the heat of hydration,reduce the activity of the silica alkali reaction in the aggregate,reduce the cost,the filling effect of the micro aggregate and the two hydration,so as to make the concrete structure more dense,improve the durability and crack resistance of the concrete.Compared with the traditional grade ash,the ultra-fine ash has the characteristics of high activity and more obvious water reducing effect.It has a remarkable improvement on the workability of concrete.It is a kind of high performance cement or concrete admixture.At present,there is no clear classification of the ultra-fine ash,the process is separation and grinding,and the research on the self compacting concrete is less.At present,there is no clear classification of the ultra-fine ash,and the research on the self compacting concrete is less.The research on the high content ultra-fine ash self compacting concrete(UFASCC)is carried out in this paper to improve the performance and green degree of the material.The specific contents are as follows:(1)XRD,SEM,EDS and particle size distribution were used to test the composition analysis,micromorphology,composition analysis and particle size distribution of ultra-fine ash of ultra-fine ash in to Huang power plant.The study shows that the main difference between ultra-fine ash and I grade ash is the difference in particle size distribution.The particle size of ultra-fine ash particles is mostly spherical particles about 2μm,while the grade-I ash is 20μm and most of them are around 6μm,and the main energy spectrum elements of ultra-fine ash and I grade ash are Si,Al,O,Fe,Ca,Ti,C and other elements,fly ash is a substance rich in Si and Al.The main components of XRD phase analysis are mullite,quartz and hematite.(2)The rheological properties and thixotropic properties of ultra-fine grout cement paste were studied by using the Anton MCR-102 rotational rheometer.The results show that:The results showed that:①the linear relationship between ultra-fine ash and grade-I ash paste rheological curve is more significant,basically showing the characteristics of Bingham fluid.But when the ultra-fine ash content is 60%or more,the linear relationship between the shear stress and the shear rate is not significant,and the H-B model is more suitable.②when the amount of ultra-fine ash is in the range of 0～20%,and for grade-I fly ash,when the amount of fly ash is in the range of 0～50%,the influence of the mixing amount of concrete working fly ash can not be considered as an important object.③Grade-I fly ash content in the range of 0～40%,the thixotropic value of the slurry is more than 80%,that is,the ability to restore the original shape after the destruction of the structure is stronger,and its thixotropic value is more stable in the range of 30%～40%;while the amount of ultra-fine ash is in the range of 0～20%,the thixotropic value of the slurry is larger and more than 90%.Although the rheological properties of high content superfine ash are less than that of grade-I ash with the same content,the thixotropy is better than the grade-I ash with the same amount.(3)the strength increasing rule of ultra-fine ash self compacting concrete was studied.The study shows that:①The strength of the superfine ash self compacting concrete(cube compressive strength,splitting tensile strength and flexural strength)is better than the strength of I grade ash self compacting concrete under the condition of the amount of fly ash.In the range of 14d-28d age,the compressive strength and splitting tensile strength of UFASCC increase rapidly,but at the age of 28d-56d,the compressive strength and splitting tensile strength of UFASCC increase steadily compared with I grade ash self compacting concrete(IFASCC),while the flexural strength of the superfine ash self compacting concrete increases faster;②the flexural strength,splitting tensile strength and flexural strength of UFASCC40%with more replacement of cement in the early stage are lower than that of UFASCC20%,but with the development of the hydration of fly ash,the later strength increases rapidly,and the difference of flexural strength,splitting tensile strength and flexural strength in the later period is little,and there is even a trend that will exceed or exceed UFASCC20%,the results show that the high content fly ash is a kind of green concrete with excellent mechanical properties.It can improve the green degree of self compacting concrete.However,whether the high dosage will produce strength reduction phenomenon still needs to be tested for longer age.(4)The microstructure of SEM,XRD and 28d pore structure of ultra-fine ash self compacting concrete was tested.The research shows that the mechanical properties of the composites can effectively verify the mechanical properties and provide the basis for the high-strength self compacting concrete. |
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