Acoustic Emission Test Of Marble Powder Concrete

In this paper,based on acoustic emission technology,uniaxial compression tests were carried out on marble powder concrete prepared by cement substitution method and fine aggregate substitution method.The mechanical performance of marble powder concrete was tested.At the same time,the fracture development process and law of marble powder concrete under two alternative methods were analyzed through acoustic emission(AE)signal parameters,and the compression fracture form and crack propagation of marble powder concrete were discussed.Behavior.The research results can provide reference for theoretical research and practical engineering application of marble powder concrete.The results showed that:(1)When marble powder is used to replace cement,as the substitution ratio increases,the concrete slump increases and the fluidity increases.When marble powder is used to replace fine aggregate,as the replacement ratio increases,the concrete slump decreases and the fluidity becomes poor.The compressive strength of marble powder concrete with cement substitution method decreases with the increase of replacement ratio at all ages,and the strength loss rate decreases with the extension of curing time.When the replacement ratio is 15%,the 28-day strength loss rate is the highest at 6.2%.The compressive strength of marble powder concrete with fine aggregate substitution method increases with the increase of marble powder substitution ratio at all ages,and the strength improvement effect is most significant at 3 days.(2)According to the analysis of acoustic emission parameters,the compression failure process of marble powder concrete under the two alternative methods is similar to that of plain concrete,and can be divided into three stages.The acoustic emission activity of marble powder concrete with cement substitution method is higher at the initial stage of loading,and the relative stress at the time of critical instability failure decreases.When the replacement ratio is 15%,the relative stress decreases by 4.2%.The relative stress of marble powder concrete with fine aggregate substitution method at the time of critical instability failure increases,and when the substitution ratio is 25%,it is 6.6% higher than that of plain concrete.(3)Acoustic emission RA-AF correlation analysis shows that tensile failure is the main fracture mode of marble powder concrete under the two alternative methods.When the cement substitution method is adopted,as the substitution ratio of marble powder increases,the proportion of tensile mode cracks in stages I and II decreases,and the proportion in stage III increases,and the failure characteristics gradually change from brittle to ductile.When the fine aggregate substitution method is adopted,the proportion of tensile cracks increases with the increase of the replacement ratio in stages I and II,and gradually decreases in stage III,and the brittleness gradually increases.(4)The acoustic emission b-value analysis method shows that the fluctuation range of b-value of marble powder concrete with cement substitution method increases with the increase of the substitution ratio.Steady growth.With the increase of the substitution ratio of fine aggregate substitution method marble powder concrete,the fluctuation range of the acoustic emission b value of the specimen decreases,and tends to fluctuate horizontally at 40-140 s,and the high-energy unstable micro-cracks decrease.Establish the damage evolution model of marble powder concrete in connection with AE cumulative counting.The results show that when marble powder is used to replace less than 15% cement,the damage development of marble powder concrete is relatively slow in the middle stress stage(relative stress 20%-70%),and the damage development is accelerated in the late stress stage.When marble powder replaces fine aggregate,the damage degree of the specimen is higher than that of plain concrete at the initial stage of loading,and the degree of damage development decreases after the relative stress reaches 30%.