Research On Flexural Fracture And Acoustic Attenuation Characteristics Of Basalt Fiber Reinforced Concrete Based On Acoustic Emission Parameters

With the increasing demand for new building materials at home and abroad,fiber reinforced concrete has been widely used and valued.Further research on the performance of fiber reinforced concrete is needed.At present,many scholars have done a lot of research on steel fiber reinforced concrete and polypropylene fiber reinforced concrete,but there is less research on basalt fiber reinforced concrete.Acoustic emission is an important nondestructive testing method,which has many advantages,such as high sensitivity,timely response,and can realize online monitoring,the whole cycle in the field of material and structural health monitoring has broad prospects.Compared with other non-destructive testing technology,acoustic emission detection technology is for its own phenomenon of the material itself,and other nondestructive monitoring technology is often detected,the response of materials and conditions such as ultrasonic nondestructive testing.At present,the study of acoustic emission characteristics of basalt fiber reinforced concrete has not appeared.So this article uses the basalt fiber reinforced concrete as the research object,the acoustic emission testing technology as a means of research,study on the mechanical properties of basalt fiber reinforced concrete and acoustic emission features,explore the fracture mechanism of fiber reinforced concrete and damage law,provide basic data and theoretical reference for the promotion and application of basalt fiber reinforced concrete emission technology in the field of concrete structure health monitoring.The main research work in this paper includes:(1)Three groups of basalt fiber reinforced concrete beams with different ages were made,and the plain concrete beams with the same age were used as the contrast group,and a total of 18 rectangular beams with the same size were tested.The four point bending test was carried out to obtain the ultimate flexural strength of the materials at different ages.The results showed that with the development of age,the reinforcement effect of fiber was increased,and the strength of concrete at 7 days,14 days and 28 days increased by 5.53%,6.10% and 8.33%,respectively.(2)Based on the statistical analysis of the acoustic emission parameters of the specimen,the fracture process of concrete specimen is analyzed.The whole fracture process can be divided into three stages,each of which corresponds to different acoustic emission characteristics.These characteristics reflect the different stress state of concrete and the corresponding expansion of internal cracks,and verify the applicability of acoustic emission monitoring of basalt fiber reinforced concrete.Based on the characteristic parameters of acoustic emission,the reinforcing mechanism and reinforcing effect of the fiber are discussed.(3)In view of the statistical parameters of acoustic emission,through compared with the corresponding stress analysis,the analysis results show that statistic characteristics of acoustic emission parameters can be used to characterize fracture prediction analysis of basalt fiber reinforced concrete materials.In addition,extract the new AE characteristic parameters,namely the maximum information entropy.The maximum information entropy can be used to analyze the fracture precursor of the material.In the process of concrete fracture,the average frequency(AF)and RA value of acoustic emission characteristic statistics are used to analyze the internal crack.(4)According to the propagation and attenuation of acoustic emission signal in basalt fiber reinforced concrete,three identical reinforced concrete cantilever beams were fabricated.Through the study of the Fourier transform of the signal and parameter extraction,summarizes the acoustic attenuation law.The results show that the acoustic emission signal amplitude with distance transmission into quadratic function attenuation trend;acoustic emission energy and wave velocity exponential function attenuation trend;for acoustic emission frequency attenuation,fast attenuation of the high-frequency part,and caused an increase in frequency distribution between the first and two order frequency of structure.With the propagation of acoustic signals,the frequency distribution of each frequency band is greatly reduced.