Research On Frost-resistance Of New Liquid Fly Ash

New liquid fly ash is a kind of lightweight roadbed backfill material mixed with cement,lime,a large amount of fly ash and water.It is inexpensive,convenient to obtain materials,and can effectively improve the inability to compress the backfill part of the roadbed.Real problems are widely used in actual projects.Roadbed materials often face the problem of freeze-thaw damage in practical engineering in cold areas.The frost resistance of the materials has become particularly important.For this reason,many domestic and foreign scholars have conducted a lot of research on the frost resistance of roadbed materials.In view of the fact that there is little research on the frost resistance of fresh liquid fly ash in China,this paper studies and determines the frost resistance of fresh liquid fly ash to meet the needs of actual projects and lay the foundation for future promotion.According to the relevant research results,determine the mix ratio for the freeze resistance study of new liquid fly ash,and conduct freeze-thaw cycle tests on specimens with different mix ratios.Study the appearance changes of specimens under freeze-thaw damage,obtain quality loss through experiments Rate,compressive strength loss rate and relative dynamic elastic modulus;study and analyze the influence of freeze-thaw times,cement and lime content on various indexes of frost resistance;determine the fitting relationship between strength and ultrasonic wave velocity under freeze-thaw cycles;determine each fit The maximum freeze-thaw times of the ratio,and the rough set theory is used to analyze the influence weights of the three influencing factors of freeze-thaw cycles,cement content,and lime content on the frost resistance of new liquid fly ash.The main conclusions obtained in this study are as follows:?1?The appearance of the specimen is damaged under the freeze-thaw cycle,and the damage law is obvious.At the beginning of freezing and thawing,the compressive strength loss rate,relative dynamic elastic modulus and mass loss rate of the specimens changed greatly.As the number of freeze-thaw cycles increases,the range of changes slowly slows down and stabilizes.?2?When the cement content is increased from 4%to 8%,it can effectively improve the mass loss rate,compressive strength loss rate and relative dynamic elastic modulus of new liquid fly ash under the freeze-thaw cycle,and increase the maximum freeze-thaw times;lime When the content increases from 0 to 4%,it can effectively reduce the mass loss rate,the compressive strength loss rate,increase the relative dynamic elastic modulus,and increase the maximum number of freeze-thaw cycles.The improvement effect is not obvious when increasing from 4%to 8%.?3?The linear fit of ultrasonic wave velocity and compressive strength is 0.993,which is excellent.In actual engineering,the simple formula y=9×10^-4x can be roughly calculated,and the error is within 6%.?4?The mix ratio of 6:4:90 should be chosen for ordinary highway;Expressway should choose 8:4:88 as the construction mix ratio.?5?Rough set theory analysis shows that among the mass loss rate,compressive strength loss rate and relative dynamic modulus of elasticity,the weight coefficient of freeze-thaw cycles is the largest,followed by its own material factors.