scholarly journals Acoustic Emission and Ultrasonic Characteristics in the Failure Process of Cemented Waste Concrete-Coal Gangue Backfilling (CWCGB) under Uniaxial Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Guorui Feng ◽  
Tingye Qi ◽  
Xianjie Du ◽  
Zehua Wang ◽  
Yujiang Zhang
Keyword(s):  
Acoustic Emission ◽  
Ultrasonic Wave ◽  
Wave Velocity ◽  
Failure Process ◽  
Coal Gangue ◽  
Uniaxial Loading ◽  
Rapid Decline ◽  
Ultrasonic Wave Velocity ◽  
Waste Concrete ◽  
Gangue Backfilling

The acoustic emission (AE) characteristics, change law of the ultrasonic velocity, and internal failure mode of cemented waste concrete-coal gangue backfilling (CWCGB) with 600 days of curing time were studied under uniaxial loading conditions. Waste concrete particles of 5 mm acting as fine aggregates substituted for 30% and 50% fine coal gangue in the cemented coal gangue backfilling (CGB). AE was used to test the ring count and changing rule of the accumulated energy, locate the event for positioning, and calculate the number of events. The average ultrasonic wave velocity was measured via an ultrasonic detector. The characteristics of the microfractures were observed via a scanning electron microscope. The results showed that the specimens with 30% and 50% waste concrete replacement rates underwent ultrasonic wave velocity stabilization and a rapid decline stage under uniaxial compression; for the former case, the decline started earlier. The AE ring count attained peaks at the pore compression stage, yield stress point, stress peak value, and residual stress stage with no added waste concrete and 30% and 50% waste concrete substitution rates. The value and consequent frequency of the ringing count peak and cumulative energy slope increased with increasing waste concrete substitution rate. A microcrack was observed at the interfacial transition zone between the cement paste and gangue owing to the alkali-aggregate reaction effect. However, a better bonding performance was exhibited by the waste concrete particles and paste.

Study on the AE Characteristics and Wave Velocity of Concrete during the Total Failure Process

2011 ◽  
Vol 368-373 ◽  
pp. 2491-2494
Author(s):  
Xing Dong Zhao ◽  
Jie Liu ◽  
Shan Chuan Cao ◽  
Shi Da Xu
Keyword(s):  
Ultrasonic Wave ◽  
Wave Velocity ◽  
High Speed ◽  
Failure Process ◽  
Compressive Loading ◽  
Initial Crack ◽  
Visual Observation ◽  
Emission Characteristic ◽  
Ultrasonic Wave Velocity ◽  
Ae Counts

This paper introduces an example on AE monitoring and ultrasonic wave velocity measurement of concrete (C20). Experiment on AE characteristic of the full failure process of concrete is carried out on the pressing machine. AE sensors can be surface mounted. A system (the 8-channels, high-speed acquiring and analyzing AE signal), called HUS (Hyperion Ultrasonic System), was employed to acquire and record AE characteristics. AE signals were recorded during loading (fracture propagation) subject to the uniaxial compressive loading until failure. Using a simplex location algorithm allows AE event location from first arrival times to be determined by the AE sensors. The mechanical properties of concrete and acoustic emission characteristic, including the full stress-strain curves, AE counts, and AE rate and ultrasonic wave velocity, were obtained. The relations among AE counts, AE rate, stress levels, ultrasonic wave velocity and time are analyzed in detail. This paper reports AE observations made with an array of this new high-fidelity. Crack initiation and crack propagation due to the uniaxial compressive loading were monitored for AE activity and compared with visual observation. Meanwhile, stress changing influence the wave velocity of concrete; with the initial crack expands, up to the rock sample failure, the wave velocity falls gradually. Some insight into the percentage of AE events that must actually be detected to describe the health of concrete sample was gained.

The evolution of structure properties of vegetation concrete under freeze–thaw cycles

2020 ◽  
pp. 002072092093036
Author(s):  
Jiazhen Gao ◽  
Mingtao Zhou ◽  
Wennian Xu ◽  
Daxiang Liu ◽  
Jian Shen ◽  
...  
Keyword(s):  
Water Content ◽  
Ultrasonic Wave ◽  
Wave Velocity ◽  
Engineering Students ◽  
Cement Hydration ◽  
Electrical Engineering ◽  
Ultrasonic Wave Velocity ◽  
Freeze Thaw ◽  
Microstructural Parameters ◽  
Thaw Cycle

Vegetation concrete is a typical artificial composite soil commonly used for ecological restoration on slopes. The strength and stability of vegetation concrete would be reduced when it is used in areas where freeze–thaw cycles occur frequently. For exploring the changes of structural properties of vegetation concrete under freeze–thaw cycles, an indoor simulation experiment of vegetation concrete samples containing 25 and 30% water content was carried out, so as to test the changes of specimen surface, volume, ultrasonic wave velocity, shearing strength, and microscopic structure. The microstructural parameters were analyzed quantitatively with Image-Pro Plus software. The experimental results indicated that as cycles of freeze–thaw grow, the macroscopic changes of samples included steadily rising surface crack rate, increasing first and then decreasing volume, greatly reducing ultrasonic wave velocity and gradually decreasing shear strength. The inner structure of samples slowly deteriorated from overall dense to dispersed with decreasing cement hydration crystals, pores resulting from dispersion and destruction of bulky grains, higher surface porosity, and smoother particles in microscopic aspect. When compared with samples containing 25% water content, the microstructure of the 30% water content sample was more affected by the freeze–thaw cycle, and its structural weakening effect was more obvious. Reduced cement hydration crystals, lower inter-particle bonding force, and increase in the number of large pores were the main causes of degradation of vegetation concrete structure. Electrical engineering students can refer to the analysis methods in this paper to evaluate the structural performance of any electrical engineering material.

scholarly journals Texture and Cross Slip Effects on Ultrasonic Wave Velocity Changes Under Simple and Pure Shear States.

2001 ◽  
Vol 67 (660) ◽  
pp. 1402-1408 ◽  
Author(s):  
Shihua TANG ◽  
Michiaki KOBAYASHI ◽  
Setsuo MIURA ◽  
Hiroryuki FUJIKI ◽  
Kazuya IWABUCHI ◽  
...  
Keyword(s):  
Ultrasonic Wave ◽  
Wave Velocity ◽  
Pure Shear ◽  
Cross Slip ◽  
Ultrasonic Wave Velocity ◽  
Slip Effects ◽  
Velocity Changes
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