scholarly journals Effect of Silica Fume in Concrete on Mechanical Properties and Dynamic Behaviors under Impact Loading

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3263 ◽  
Author(s):  
Shijun Zhao ◽  
Qing Zhang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Silica Fume ◽  
Impact Loading ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Dynamic Tensile Strength ◽  
Dynamic Behaviors

The effect of silica fume (SF) in concrete on mechanical properties and dynamic behaviors was experimentally studied by split Hopkinson pressure bar (SHPB) device with pulse shaping technique. Three series of concrete with 0, 12%, and 16% SF as a cement replacement by weight were produced firstly. Then the experimental procedure for dynamic tests of concrete specimens with SF under a high loading rate was presented. Considering the mechanical performance and behaviors of the concrete mixtures, those tests were conducted under five different impact velocities. The experimental results clearly show concrete with different levels of SF is a strain-rate sensitive material. The tensile strength under impact loading of the tested specimens was generally improved with the increasing content of SF levels in concrete. Additionally, the tensile strength under impact loading of the concrete enhances with the increase of the strain rates. Finally, failure modes, dynamic tensile strength, dynamic increase factor (DIF), and critical strain are discussed and analyzed. These investigations are useful to improve the understanding of the effect of SF in concrete and guide the design of concrete structures.

scholarly journals Effects of Temperature and Water on Mechanical Properties, Energy Dissipation, and Microstructure of Argillaceous Sandstone under Static and Dynamic Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Rongrong Zhang ◽  
Dongdong Ma ◽  
Qingqing Su ◽  
Kun Huang
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Physical And Mechanical Properties ◽  
P Wave ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Sandstone Specimen

RMT-150B rock mechanics and split Hopkinson pressure bar (SHPB) devices were adopted to investigate the physical and mechanical properties, energy dissipation, and failure modes of argillaceous sandstone after different high temperatures under air-dried and saturation states. In addition, SEM and EDS tests were conducted to investigate its microstructure characteristics. Results showed that both the P-wave velocity and density of argillaceous sandstone specimen decreased with the increase of high temperature, while its porosity increased. Compared with static stress-strain curves, there was no obvious compaction stage for dynamic stress-strain curves, and the decrease rate of dynamic curves after peak strain was obviously slow compared with static curves. Both the static and dynamic strengths of argillaceous sandstone specimens decreased with increasing temperature, and the critical temperature point for the strength of argillaceous sandstone was 400°C. At the same temperature, the specific energy absorption under air-dried state was generally smaller compared with that under saturated state. Both the strain rate and temperature showed significant effect on the failure mode. After 100∼1000°C heat treatment, the granular crystals of the clastic structure gradually became larger, and both the number and average size of the original pores decreased, resulting in the deterioration of mechanical properties of argillaceous sandstone specimen.

scholarly journals Dynamic tensile strength enhancement of concrete in split Hopkinson pressure bar test

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878230 ◽  
Author(s):  
Jingyi Chen ◽  
Da Xiang ◽  
Zhihua Wang ◽  
Guiying Wu ◽  
Genwei Wang
Keyword(s):  
Tensile Strength ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Dynamic Tensile Strength ◽  
Concrete Material ◽  
Split Hopkinson ◽  
Bar Test ◽  
Concrete Materials ◽  
Pressure Bar

Split Hopkinson pressure bar technique has been widely used to measure the dynamic tensile strength of concrete materials. Most experimental results show that the tensile strength of concrete material increases with strain rates. However, the dynamic tensile strength derived from the split Hopkinson pressure bar test is affected by lateral inertia confinement, which may lead to the overestimation of dynamic mechanical properties of concrete materials. The true dynamic characteristics of concrete materials are not actually shown by experimental data. It is impossible to completely eliminate the influence of lateral inertia confinement in split Hopkinson pressure bar tests. In this study, a rate-insensitive material model is used in commercial finite element software to study how the lateral inertia confinement affects the dynamic tensile strength of concrete material at strain rates between 30/s and 150/s. Comparison of finite element results and split Hopkinson pressure bar test results shows that the dynamic tensile strength enhancement of concrete materials is strongly influenced by the inertial effect. The dynamic increase factor of concrete materials which remove the influence of lateral inertia confinement in split Hopkinson pressure bar tests can reflect the true dynamic characteristics of concrete materials. It is also found that the influence of lateral inertia confinement is related to the size of the specimen.

scholarly journals The Coupled Effect of Loading Rate and Grain Size on Tensile Strength of Sandstones under Dynamic Disturbance

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Miao Yu ◽  
Chenhui Wei ◽  
Leilei Niu
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Failure Modes ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Hopkinson Pressure Bar ◽  
Loading Rates ◽  
Grain Sizes ◽  
Average Grain Size

It is of significance to comprehend the effects of rock microstructure on the tensile strength under different loading rates caused by mining disturbance. So, in this paper, three kinds of sandstones drilled from surrounding rocks in Xiao Jihan Coal to simulate the in situ stress state, whose average grain size is 30 μm (fine grain, FG), 105 μm (medium grain, MG), and 231 μm (Coarse grain, CG), are selected with the calculation of optical microscopic technique and moreover processed to Brazilian disc (BD) to study the mechanical response of samples. The dynamic Brazilian tests of samples with three kinds of grain sizes are conducted with the Split Hopkinson Pressure Bar (SHPB) driven by pendulum hammer, which can produce four different velocities (V=2.0 m/s, 2.5 m/s, 3.3 m/s, and 4.2 m/s) when the incident bar is impacted by pendulum hammer. The incident wave produced by pendulum hammer is a slowly rising stress wave, which allows gradual stress accumulation in the specimen and maintains the load at both ends of the specimen in an equilibrium state. The results show that the dynamic strength of three kinds of BD samples represented loading rates dependence, and FG sandstones are more sensitive for loading rates than MG and CG samples. Moreover, the peak strength is observed to increase linearly with an increasing stress rates, and the relationship between the dynamic BD strength and stress rates can be built through a linear equation. Finally, the failure modes of different grain sizes are discussed and explained by microfailure mechanism.

Dynamic Tensile Test of Coal, Shale and Sandstone Using Split Hopkinson Pressure Bar

2010 ◽  
Vol 1 (2) ◽  
pp. 24-37 ◽  
Author(s):  
Kaiwen Xia ◽  
Sheng Huang ◽  
Ajay Kumar Jha
Keyword(s):  
Tensile Strength ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Static Strength ◽  
Test Method ◽  
Hopkinson Pressure Bar ◽  
Dynamic Tensile Strength ◽  
Sandstone Sample ◽  
Rock Samples ◽  
Sandstone Rock

The dynamic tensile strength plays a pivotal role in rock fragmentation affecting the overall economics under the present ‘Mine to Mill Concept’. In this paper, a modified SHPB technique and Brazilian test method is presented to test the dynamic tensile strength of coal, shale and sandstone rock samples collected from three opencast mines of Coal India Limited and is compared with the static strength value. The dynamic tensile strength of coal and rock is much higher than static strength and tensile strength of coal and rock samples increase with loading rate. The result shows that the dynamic strength of the coal sample is 1.5 times higher than static strength and the dynamic strength of the sandstone sample is 3 times higher than the static strength.

Dynamic Tensile Test of Coal, Shale and Sandstone Using Split Hopkinson Pressure Bar

2012 ◽  
pp. 188-202
Author(s):  
Kaiwen Xia ◽  
Sheng Huang ◽  
Ajay Kumar Jha
Keyword(s):  
Tensile Strength ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Static Strength ◽  
Test Method ◽  
Hopkinson Pressure Bar ◽  
Dynamic Tensile Strength ◽  
Rock Samples ◽  
Split Hopkinson ◽  
Pressure Bar

The dynamic tensile strength plays a pivotal role in rock fragmentation affecting the overall economics under the present ‘Mine to Mill Concept’. In this paper, a modified SHPB technique and Brazilian test method is presented to test the dynamic tensile strength of coal, shale and sandstone rock samples collected from three opencast mines of Coal India Limited and is compared with the static strength value. The dynamic tensile strength of coal and rock is much higher than static strength and tensile strength of coal and rock samples increase with loading rate. The result shows that the dynamic strength of the coal sample is 1.5 times higher than static strength and the dynamic strength of the sandstone sample is 3 times higher than the static strength.

scholarly journals Effect of strain rate and high temperature on the tensile mechanical properties of coal sandstone

2019 ◽  
Vol 23 (Suppl. 3) ◽  
pp. 927-933
Author(s):  
Zhong Zhao ◽  
Mao-Xian Biao ◽  
Ming Li ◽  
Lian-Ying Zhang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
High Temperature ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Test System ◽  
Indirect Tensile Strength ◽  
Hopkinson Pressure Bar ◽  
Indirect Tensile

The Split-Hopkinson pressure bar test system with the MTS652.02 high temperature furnace and the 50 mm diameter are used to investigate the dynamic tensile mechanical properties of coal sandstone for the first time. Brazilian tests at high loading rates are conducted at ambient temperature and after heat treatment at 800?C. The effect of the strain rate on the tensile mechanical properties is analyzed using the SEM. The results show that after heat treatment at 800?C, the dynamic indirect tensile strength of sandstone increases with the increase of strain rate. Due to the effect of thermal melting and evaporation, after treatment at 800?C, the edges of the internal cracks in the sandstone become rough and lead to more defects. This makes the dynamic indirect tensile strength of the samples at room temperature greater than that at high temperature under the same strain rate. After heat treatment at 800?C, as the strain rate increases, the damage morphology of sandstone changes from large arc-shaped unilateral tensile faces to small granular detrital fragments; the extent of damage gradually increases at the same time.

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