Study On The Hydration Mechanism Of Fly Ash Active Aggregate In Mortar

This article mainly discusses the effects of different curing temperatures,different fly ash replacement rates and age changes on the mechanical properties of the Ⅱ fly ash equal volume replacement fine aggregate mortar and the hydration of the fly ash.Through mechanical performance experiment,non-evaporating water content experiment,fly ash hydration degree experiment,scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)experiment,combined with macro and micro,systematically studied the hydration mechanism of fly ash active aggregate in mortar and quantified the degree of hydration.I hope to provide a theoretical basis for the further application of fly ash fine aggregate mortar.The compressive strength,flexural strength and average ultrasonic velocity were tested.The test results show that the long-term compressive strength under normal temperature curing increases with the increase of the replacement rate,and the best flexural strength is the replacement rate of 35%;The increase in temperature can obviously enhance the early mechanical properties of the sample,but the time when the negative effect of high temperature appears is also earlier,and the adverse effect on the long-term strength is more obvious.The increase in the replacement rate helps to alleviate the decrease in intensity caused by negative temperature effects.The non-evaporating water content was tested.The test results show that under normal temperature curing,the non-evaporating water content increases with age,and has an obvious positive function relationship with the mechanical properties;under 50 ℃ curing,the replacement rate of 15%can significantly increase the non-evaporating water content;80℃ Although curing can increase the non-evaporating water content of the sample at 1d,it will cause a significant decrease in 1-7d.The degree of hydration of fly ash was tested.The test results show that the effect of curing temperature is mainly in the early stage of hydration and the law that the degree of hydration of fly ash decreases with the increase of replacement rate cannot be changed in the long term;Under 50℃curing,35%is the critical replacement rate at 1d,less than 35%is mainly pozzolanic effect,and more than is mainly micro-aggregate effect.The degree of hydration of fly ash is related to the content of surface elements,but has no obvious relationship with mechanical properties.This study provides a scientific basis for the scientific use of fly ash,the effective use of its micro-aggregate effect as an active aggregate,the improvement of the scientific design of the mix ratio of fly ash and the realization of macroscopic performance prediction.