Effects Of Hydrothermal Combination On The Activity Of Fly Ash And Its Mechanism

In China,the ash inventory is large and the annual growth rate is high,so a large amount of fly ash is seldom fully utilized,which not only causes pollution to the environment,but also is a waste of resources.Fly ash has pozzolanic activity,but its chemical stability is still good under normal temperature and pressure.Only after 1 month or more under the action of the activator,its chemical activity can be more obvious.In addition,the low quality of fly ash in most power plants in China hinders its utilization of high performance.How to fully stimulate the potential activity of fly ash has been the focus of high performance concrete.Taking ? and ? fly ash as the research object,study the activity of fly ash in the water under the action of heat excitation characteristics.? pulverized coal is divided into the experimental group and the control group,with 10%,20%,30%,40% of the content such as quality-instead of cement fly ash cement composite mortar specimen.In the experimental group,autoclave curing was carried out at 1.3mpa and 180?.After 10 hours of autoclave curing,standard curing was carried out for 7d,60 d and 90 d,respectively.The control group was directly treated with standard curing,the curing temperature was 20±5?,the relative humidity was above 95%,and the curing lasted for 7d,60 d and 90 d.? grade fly ash with same dosage of 10%,20%,30%,40% of quality instead of cement mortar specimen,such as autoclaved curing after 10 h standard curing,curing respectively 60 d,90 d,120 d.The mechanical properties of bending strength and compressive strength were determined and analyzed macroscopically,and the internal mechanism was studied by means of XRD and SEM.The influence of the changes of age,content and particle size on mechanical properties was investigated and analyzed mathematically.The composition,morphology and microstructure of hydration products of fly ash-cement system were observed at the micro level.The experimental results show that the hydrothermal synthesis method greatly improves the strength of fly ash activity.Compared with the control group without autoclaved,the experimental group can improve the early strength by 110%~120%.The strength of mortar specimens is also different under the condition of different content of the same age,which shows that with the increase of content,the strength tends to increase first and then decrease,and the strength is maximum at the content of 20%-30%,which indicates that the fly ash has the best effect when it is mixed with 20%-30% of the same quality instead of cement.Under the condition of the same content and different ages,the fly ash activity gradually increases with the age extension,indicating that fly ash is a kind of material with slow hydration reaction,relatively dense structure and not easy to be destroyed.From the microscopic test,it can be seen that the ash reaction produces ettringite and c-s-h gelling material,filling the voids,thus improving the strength.