scholarly journals Research on the Mechanical Performance of Carbon Nanofiber Reinforced Concrete under Impact Load Based on Fractal Theory

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 387
Author(s):  
Wei Xia ◽  
Jinyu Xu ◽  
Liangxue Nie
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Toughness ◽  
Strain Rate ◽  
Carbon Nanofiber ◽  
Impact Load ◽  
Fractal Theory ◽  
Rate Level ◽  
Dynamic Compressive Strength ◽  
The Impact

The research is focused on the dynamic compressive strength, impact toughness and the distribution law of fragmentation size for the plain concrete and the carbon nanofiber reinforced concrete with four fiber volume contents (0.1%, 0.2%, 0.3% and 0.5%) under impact load by using the Φ100 mm split-Hopkinson pressure bar. Based on the fractal theory and considering the micropore structure characteristics of the specimen, the impact of the strain rate and the dosage of carbon nanofibers on the dynamic mechanical performance of concrete is analyzed. According to the results, both the dynamic compressive strength and the impact toughness increase continuously with the improvement of the strain rate level at the same dosage of fiber, showing strong strain rate strengthening effect; at the same strain rate level, the impact toughness increases gradually with the increase in the fiber dosage, while the dynamic compressive strength tends to increase at first and then decrease; the distribution of the fragmentation size of concrete is a fractal in statistical sense, in general, the higher the strain rate level, the higher the number of fragments, the lower the size, and the larger the fractal dimension; the optimal dosage of carbon nanofibers to improve the dynamic compressive strength of concrete is 0.3%, and the pore structure characteristics of carbon nanofiber reinforced concrete exhibit obvious fractal features.

scholarly journals Dynamic Compressive Properties of Carbon Nanofibers Reinforced Concrete under Impact Load

2021 ◽  
Author(s):  
Wei Xia ◽  
Jinyu Xu ◽  
Liangxue Nie
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Impact Toughness ◽  
Strain Rate ◽  
Carbon Nanofibers ◽  
Impact Load ◽  
Dynamic Compression ◽  
Dynamic Elastic Modulus ◽  
Compressive Properties ◽  
Dynamic Compressive Strength

Abstract To explore the dynamic compressive properties of carbon nanofibers reinforced concrete (CNFC), a 100mm-diameter Split Hopkinson Pressure Bar (SHPB) was used to carry out the impact compression test respectively on the plain concrete samples and the CNFC samples with different fiber volume fractions (respectively, 0.1%, 0.2%, 0.3% and 0.5%). On this basis, the change characteristics of concrete at five different strain rate levels in dynamic compressive strength, dynamic compression deformation, impact toughness and dynamic elastic modulus of concrete were compared and analyzed. The results show that the dynamic compressive strength, dynamic compression deformation and impact toughness of concrete are enhanced by carbon nanofibers to varying degrees. Specifically, when the content of carbon nanofibers is 0.3%, its enhancement effect on dynamic compressive strength is the best; when the content of carbon nanofibers is 0.2%, it helps enhance the dynamic elastic modulus of concrete, but other content can only have the opposite effect. The dynamic compressive strength, impact toughness and dynamic elastic modulus of plain concrete and CNFC gradually increase with the increase of strain rate level, indicating the existence of significant linear relationship; although the dynamic peak strain and ultimate strain increase wholly with the increase of strain rate, there is no obvious linear correlation between them. In addition, the micro test results show that the addition of an appropriate amount of carbon nanofibers help exert the small size effect, strengthen crack resistance and improve the microstructure of the matrix, effectively enhancing the dynamic compressive properties of concrete under impact load.

scholarly journals A Study of Impact Response and Its Numerical Study of Hybrid Polypropylene Fiber-Reinforced Concrete with Different Sizes

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Ninghui Liang ◽  
Ru Yan ◽  
Xinrong Liu ◽  
Peng Yang ◽  
Zuliang Zhong
Keyword(s):  
Compressive Strength ◽  
Constitutive Model ◽  
Strain Rate ◽  
Numerical Study ◽  
Polypropylene Fiber ◽  
Fiber Reinforced Concrete ◽  
Compressive Properties ◽  
Dynamic Compressive Strength ◽  
The Impact ◽  
Polypropylene Fiber Reinforced Concrete

Compressive properties of hybrid polypropylene fiber-reinforced concrete (HPFRC) with different sizes of polypropylene fibers (PPFs) under the impact load (101∼102/s) were tested by using a 74 mm diameter various cross-section split-Hopkinson pressure bar (SHPB), in which the fiber content of fine PPFs was 0.9 kg/m3 and that of coarse PPFs was 6.0 kg/m3. The effect of strain rate and PPF hybridization on the impact characteristics of HPFRC was analyzed. It is found that dynamic compressive properties, including dynamic compressive strength, dynamic compressive strength increase factor (DCF), ultimate strain, and impact toughness, increased with the increase of strain rate. Meanwhile, both fine PPFs and coarse PPFs can enhance the impact strength of concrete, and an appropriate hybridization of two sizes of PPFs in concrete was more effective than the concrete reinforced with one size of PPF. Moreover, a modified constitutive model for HPFRC was proposed based on the Holmquist–Johnson–Cook (HJC) constitutive model. Then, the numerical study of SHPB tests for HPFRC was conducted based on the modified model, which showed that the modified HJC constitutive model could well describe the dynamic stress-strain relationship of HPFRC.

scholarly journals Experimental Study on Dynamic Compression Characteristics of Red Sandstone under Wetting-Drying Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Bin Du ◽  
Haibo Bai ◽  
Minglei Zhai ◽  
Shixin He
Keyword(s):  
Compressive Strength ◽  
Fractal Dimension ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Degradation Mechanism ◽  
Impact Compression ◽  
Red Sandstone ◽  
Dynamic Compressive Strength ◽  
The Impact

To study the influence of wetting-drying cycles on dynamic mechanical properties of rock masses, the impact compression tests of red sandstone samples were carried out by using a split Hopkinson pressure bar (SHPB) apparatus with a diameter of 50 mm. The results showed that under the same number of wetting-drying cycles, the dynamic compressive strength of red sandstone increased exponentially with the strain rate, and the sensitivity of the strain rate decreased with the increase of wetting-drying cycles. The deterioration effect of wetting-drying cycles was significant, and the dynamic and static compressive strength decreased with the increase of wetting-drying cycles; the higher the strain rate, the stronger the sensitivity to wetting-drying cycles. Besides, the influence of wetting-drying cycles and strain rate was comprehensively studied, and the equation of dynamic compressive strength of red sandstone was obtained. After different wetting-drying cycles, the fractal characteristics of red sandstone dynamic fragmentation were obvious, and the fractal dimension was 2.02–2.80, and the fractal dimension increased logarithmically with the strain rate. Finally, the internal microstructure of red sandstone after different wetting-drying cycles was analyzed, and the degradation mechanism of the rock by the cycles was discussed.

scholarly journals Behavior and strength of reinforced reactive powder concrete beams under impact loadings

2018 ◽  
Vol 7 (4) ◽  
pp. 2753
Author(s):  
Ibtihal Fadhil ◽  
Ayad K. Kadhem ◽  
Nisreen Salih
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Beams ◽  
Impact Load ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Reactive Powder Concrete ◽  
Reactive Powder ◽  
The Impact

Reactive powder concrete is a new concrete that has been used in recent years because of many advantages. The use of reactive powder concrete in structural elements such as beams provides higher compressive strength, higher modulus of elasticity, durable concrete and increasing the concrete ductility, so that the concrete has high resistance against tensile stress. The experimental tests of the reinforced concrete beams under the effects of impact loadings are investigated in this paper. The parameters being adopted in present paper are steel fiber of (1, 1.5 and 2%) by volume, dropped mass and height of drop. The reinforced concrete specimens were tested under impact load by one strike only. The test results indicate that the impact force increased when the compressive strength of concrete increased that when the steel fiber ratio becomes more and the deflection has become less.  

Effect of combined drink cans and steel fibers on the impact resistance and mechanical properties of concrete

2020 ◽  
Vol 14 (2) ◽  
pp. 6734-6742
Author(s):  
A. Syamsir ◽  
S. M. Mubin ◽  
N. M. Nor ◽  
V. Anggraini ◽  
S. Nagappan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Resistance ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Indirect Tensile ◽  
The Impact

This study investigated the combine effect of 0.2 % drink cans and steel fibers with volume fractions of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% to the mechanical properties and impact resistance of concrete. Hooked-end steel fiber with 30 mm and 0.75 mm length and diameter, respectively was selected for this study.  The drinks cans fiber were twisted manually in order to increase friction between fiber and concrete. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the strength performance of concrete, especially the compressive strength, flexural strength and indirect tensile strength. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the compressive strength, flexural strength and indirect tensile strength by 2.3, 7, and 2 times as compare to batch 1, respectively. Moreover, the impact resistance of fiber reinforced concrete has increase by 7 times as compared to non-fiber concretes. Moreover, the impact resistance of fiber reinforced concrete consistently gave better results as compared to non-fiber concretes. The fiber reinforced concrete turned more ductile as the dosage of fibers was increased and ductility started to decrease slightly after optimum fiber dosage was reached. It was found that concrete with combination of 2% steel and 0.2% drink cans fibers showed the highest compressive, split tensile, flexural as well as impact strength.    

scholarly journals Predicting the behavior of reinforced concrete columns confined by fiber reinforced polymers using data mining techniques

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Sahar Y. Ghanem ◽  
Heba Elgazzar
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Compressive Stress ◽  
Compressive Strain ◽  
Concrete Columns ◽  
Steel Reinforcement ◽  
Fiber Reinforced Polymers ◽  
Stress And Strain ◽  
Fiber Reinforced ◽  
The Impact

AbstractFiber Reinforced Polymer (FRP) usage to wrap reinforced concrete (RC) structures has become a popular technology. Most studies about RC columns wrapped with FRP in literature ignored the internal steel reinforcement. This paper aims to develop a model for the axial compressive strength and axial strain for FRP confined concrete columns with internal steel reinforcement. The impact of FRP, Transverse, and longitudinal reinforcement is studied. Two non-destructive analysis methods are explored: Artificial Neural Networks (ANNs) and Regression Analysis (RA). The database used in the analysis contains the experimental results of sixty-four concrete columns under the compressive concentric load available in the literature. The results show that both models can predict the column's compressive stress and strain reasonably with low error and high accuracy. FRP has the highest effect on the confined compressive stress and strain compared to other materials. While the longitudinal steel actively contributes to the compressive strength, and the transverse steel actively contributes to the compressive strain.

The Impact Load on a Reinforced Concrete Beam

2021 ◽  
pp. 199-245
Author(s):  
Farzad Hejazi ◽  
Hojjat Mohammadi Esfahani
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beam ◽  
Impact Load ◽  
Reinforced Concrete Beam ◽  
The Impact

Effect of the Fine Recycled Aggregates on the Dynamic Compressive Behavior of Recycled Mortar

2020 ◽  
Vol 991 ◽  
pp. 62-69
Author(s):  
Sallehan Ismail ◽  
Mohamad Asri Abd Hamid ◽  
Zaiton Yaacob
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Energy Absorption ◽  
Specific Energy ◽  
Split Hopkinson Pressure Bar ◽  
Recycled Aggregates ◽  
Fine Aggregate ◽  
Peak Strain ◽  
Specific Energy Absorption ◽  
The Impact

This study aims to investigate the dynamic behavior of recycled mortar under impact loading using a split Hopkinson pressure bar (SHPB). Several mortar mixtures were produced by adding various fine recycled aggregates (FRA) to the mixture in replacement percentages of 0%, 25%, 50%, 75%, and 100% of the natural fine aggregate (NFA). The effects of strain rate on compressive strength and specific energy absorption were obtained. Results show that the dynamic compressive strength and specific energy absorption of recycled mortar are highly strain rate dependent; specifically, they increase nearly linearly with the increase in peak strain rate. However, the compressive strength and specific energy absorption of recycled mortar are generally lower than those of NFA mortar (reference samples) under similar high strain rates. The findings of this research can help researchers and construction practitioners to ascertain the appropriate mix design procedure to optimize the impact strength properties of recycled mortar for protective structural application.

Impact Behaviour of Metallic Fibre Reinforced Concrete and Mortar

1990 ◽  
Vol 211 ◽  
Author(s):  
P. Hamelin ◽  
M. Razani
Keyword(s):  
Reinforced Concrete ◽  
Strain Rate ◽  
Damage Model ◽  
Research Work ◽  
Fibre Reinforced Concrete ◽  
Stress Strain ◽  
Impact Behaviour ◽  
Experimental Apparatus ◽  
The Impact ◽  
Behaviour Law

AbstractThis research work concerns the impact behaviour of metallic fibre reinforced concrete. After a description of the experimental apparatus used, an air compressed gun, we present the main results in terms of stress–strain diagrams as a function of the strain rate. Then, we establish equations of a specific damage model which take account of the different phases of the behaviour law.

Experimental and Numerical Analysis of Qinling Mountain Engineered Rocks during Pulse-Shaped SHPB Test

2015 ◽  
Vol 16 (3-4) ◽  
pp. 165-171
Author(s):  
Shi Liu ◽  
Jinyu Xu
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Energy Absorption ◽  
Absorption Rate ◽  
Failure Modes ◽  
Dynamic Compression ◽  
Peak Strain ◽  
Compression Stress ◽  
Dynamic Compressive Strength

AbstractIn order to study the dynamic compression mechanical properties of engineering rock under high strain rate （100~102 S−1）loads, dynamic compression tests of three common engineering rocks (marble, sandstone and granite) taken from the Qinling Mountain are studied subjected to five different kinds of shock air pressure using Φ 100 mm split Hopkinson pressure bar test system improved with purple copper waveform shaper. The dynamic compression stress-strain curves, dynamic compressive strength, peak strain, energy absorption rate and elastic modulus of three rocks variation with strain rate are researched. The dynamic compression failure modes under different strain rates are analyzed. Then the three-dimensional numerical simulations of waveform shaper shaping effects and stress wave propagation in the SHPB tests are carried out to reproduce the test results. The research results show that the dynamic compression stress-strain curves show certain discreteness, and there is an obvious rebound phenomenon after the peak. With the increase in strain rate, the dynamic compressive strength, peak strain and energy absorption rate are all in a certain degree of increase, but the elastic modulus have no obvious change trend. Under the same strain rate, the dynamic compressive strength of granite is greatest while of sandstone is least. With the increase in strain rate, the margin of increase in peak strain and energy absorption rate of granite is greatest while of sandstone is least. The failure modes of the sample experience a developing process from outside to inside with the increase of strain rate.

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