Stress-Strain Characteristics of a Cement-Bentonite Mix for a Barrier System The Implication of Time and Curing

For containment and water exclusion purposes, cement-bentonite (CB) barrier walls are usually built, with certain design criteria specified for the wall to fulfill intended purposes. While permeability is believed to be the most important criterion, it can be impacted by the stress-strain properties of the wall, which define the strength and stiffness. This study investigates the influence of curing time, confinement, rate of axial deformation, and quantity of cement (mix of Portland cement (PC) and ground granulated blast furnace slag (GGBS)) on the stress-strain properties of CB slurry walls. An unconfined compressive test supported by (i.e. UCT) undrained triaxial (UUT) tests were carried out on specimens prepared from two mix-designs (differentiated by the proportion of GGBS in the cement component) and cured 7, 14, 28, 60, and 90 days. Two rates of deformation (1.0mm/min and 1.2mm/min) were examined, using a range of confining pressure (i.e., 50 - 200 kPa) in the UUT. The results reveal that varying rates of deformation and the range of confining pressures have no clear influence on the mechanical properties (e.g., deviator stress, shear strength, and stiffness) of the CB mix-designs. However, increased curing time, and the proportion of GGBS significantly improved these properties. An increased proportion of GGBS enhances early strength. Thus, further work needs to be done to establish a balance between adequate strength and adequate flexibility of CB walls in order to not compromise permeability.

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Macroscopic and Mesoscopic Mechanical Properties of Mine Tailings with Different Dry Densities under Different Confining Pressures

Geofluids ◽

10.1155/2020/8832335 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Zhi-jun Zhang ◽

Yao-hui Guo ◽

Ya-kun Tian ◽

Lin Hu ◽

Xi-xian Wang ◽

...

Keyword(s):

Numerical Simulation ◽

Coordination Number ◽

Mine Tailings ◽

Confining Pressure ◽

Simulation Software ◽

Particle Flow ◽

Dry Density ◽

Stress Strain ◽

High Confining Pressure ◽

Confining Pressures

Particle flow numerical simulation software (PFC3D) was utilized to establish the consolidated-undrained triaxial compression test numerical models of mine tailings with different dry densities to deeply investigate the macroscopic and microscopic characteristics of mine tailings in a tailing pond in Hunan Province. Comparing the results of the simulation and the laboratory experiment, the mesoscopic parameters of the particle flow numerical simulation were obtained through continuously adjusting the mesoscopic parameter with the higher degree of agreement between the stress-strain curve, the peak strength, and the elastic modulus as the determining standard. The macroscopic and microscopic characteristics of mine tailings were studied from the perspectives of stress-strain, axial strain-volume strain, coordination number, particle velocity vector, and contact force between particles. After numerous numerical tests, it was found that the PFC3D simulation results are consistent with experiment results of the dry density tailing samples under different confining pressures; compared with the high confining pressure, the simulation test results at lower confining pressures were more with that of the laboratory tests; low density and high confining pressure both have inhibitory effect on the dilatancy characteristics of triaxial samples; with the same confining pressure, the dilatancy tendency of low dry density samples is suppressed comparing with the high dry density samples. The initial coordination number of the numerical model is large, which proves that the contact degree of the model is good to some extent.

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Influence of Curing Time on the Drying Shrinkage of Concretes with Different Binders and Water-to-Binder Ratios

Advances in Materials Science and Engineering ◽

10.1155/2017/2695435 ◽

2017 ◽

Vol 2017 ◽

pp. 1-10 ◽

Cited By ~ 12

Author(s):

Jun Yang ◽

Qiang Wang ◽

Yuqi Zhou

Keyword(s):

Blast Furnace ◽

Fly Ash ◽

Blast Furnace Slag ◽

Drying Shrinkage ◽

Mineral Admixture ◽

Curing Time ◽

Cement Concrete ◽

Fly Ash Concrete ◽

Granulated Blast Furnace Slag ◽

Furnace Slag

Plain cement concrete, ground granulated blast furnace slag (GGBS) concrete, and fly ash concrete were designed. Three wet curing periods were employed, which were 2, 5, and 8 days. The drying shrinkage values of the concretes were measured within 1 year after wet curing. The results show that the increasing rate of the drying shrinkage of concrete containing a mineral admixture at late age is higher than that of plain cement concrete regardless of the wet curing time. With the reduction of wet curing time, the increment of total drying shrinkage of concrete decreases with the decrease of the W/B ratio. The negative effects on the drying shrinkage of fly ash concrete due to the reduction of the wet curing time are much more obvious than those of GGBS concrete and plain cement concrete. Superfine ground granulated blast furnace slag (SGGBS) can reduce the drying shrinkage of GGBS concrete and fly ash concrete when the wet curing time is insufficient.

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Experimental Study of Stress-Strain Characteristics of the Fly Ash Blended with Curing Agent

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.1934 ◽

2010 ◽

Vol 168-170 ◽

pp. 1934-1942

Author(s):

Zheng Shen ◽

Lan Zong ◽

Xiang Dong

Keyword(s):

Fly Ash ◽

Triaxial Compression ◽

Confining Pressure ◽

Uniaxial Stress ◽

Curing Agent ◽

Compression Tests ◽

Growth Trend ◽

Stress Strain ◽

Confining Pressures ◽

Triaxial Compression Tests

The stress-strain characteristics of the fly ash blended with curing agent was studied using uniaxial and triaxial compression tests. Curing agent JNS-2 was used as the stabilizing agents in sample preparation. Four curing agent JNS-2 contents of 3%, 6%, 9% and 12% were selected for sample preparation. UU triaxial compression tests were conducted in a range of confining pressures from 100 kPa to 300 kPa. The experimental results obtained from the laboratory tests showed that curing age, mixture ratio, compaction degree and confining pressures had significant influence on the shape of curves. Uniaxial stress-strain test results demonstrated that the latter strength and deformation characteristics of the fly ash blended with curing agent grew little and with the increase of curing agent amount and compaction factor, the curve of uniaxial stress-strain changed significantly. On the other hand, triaxial stress-strain test results indicted that the failure strain showed a partial negative growth trend with the increase of curing agent amount, and the failure stress showed a partial positive growth trend with the increase of curing agent amount. When the curve was at high confining pressure, it showed hardening type, when at low confining pressure it showed softening type.

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Effect of curing time on granulated blast-furnace slag cement mortars carbonation

Cement and Concrete Composites ◽

10.1016/j.cemconcomp.2018.04.006 ◽

2018 ◽

Vol 90 ◽

pp. 257-265 ◽

Cited By ~ 29

Author(s):

Miguel Ángel Sanjuán ◽

Esteban Estévez ◽

Cristina Argiz ◽

Daniel del Barrio

Keyword(s):

Blast Furnace ◽

Blast Furnace Slag ◽

Curing Time ◽

Slag Cement ◽

Granulated Blast Furnace Slag ◽

Cement Mortars ◽

Furnace Slag

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Numerical Simulation of SHPB Test for Concrete under Confining Pressure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.3144 ◽

2014 ◽

Vol 580-583 ◽

pp. 3144-3148 ◽

Cited By ~ 1

Author(s):

Hua Zhang ◽

Ao Yu Xie ◽

Yu Wei Gao

Keyword(s):

Strain Rate ◽

Split Hopkinson Pressure Bar ◽

Dynamic Properties ◽

Confining Pressure ◽

Hopkinson Pressure Bar ◽

Stress Strain ◽

Confining Pressures ◽

Stress States ◽

Pressure Bar ◽

The Impact

Using the HJC dynamic constitutive model, the Split Hopkinson Pressure Bar (SHPB) impact test with confining pressure for concrete was simulated in the software ANSYS/LS-DYNA. The confining pressure was simulated by applying constant pressure around the specimen. The triangle velocity wave, which has less diffusion, is used as loader in the simulation. The confining pressures used were 0MPa, 2MPa, 4MPa, 8MPa and 16MPa and the stress-strain curves were presented. The influence of confining pressure on the dynamic properties was analyzed by comparing the stress-strain curves of concrete under different stress states. The strain rate decreases sensitively as long as the confining pressure increases. By debugging the impact velocity, the stress-strain curves under the similar strain rate were obtained, which indicate the toughening and reinforcing effect with the increase of confining pressure.

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Experimental Study on Shear Strength of Saturated Remolded Loess

10.21203/rs.3.rs-156405/v1 ◽

2021 ◽

Author(s):

Jie Lai ◽

Yun Liu ◽

Yuzhou Xiang ◽

Wei Wang ◽

Jiangbo Xu ◽

...

Keyword(s):

Shear Strength ◽

Shear Rate ◽

Strain Curve ◽

Confining Pressure ◽

Cohesive Force ◽

Dry Density ◽

Stress Strain ◽

Loess Area ◽

Confining Pressures ◽

Homogeneous Composition

Abstract Loess has the characteristic of macropore, loose structure, homogeneous composition and collapsibility. It is easy to saturate when it encounters heavy rainfall and irrigation, resulting in landslides, roadbed subsidence and dam instability in the loess area. To study the influence of dry density and shear rate on shear strength of saturated remolded loess, an SLB-6A stress-strain controlled triaxial shear penetration tester was used to conduct Consolidated Undrained(CU) test in the Yan'an area. During the test, three variables of shear rate, confining pressure and dry density were controlled. The dry densities of the samples were 1.5g/cm3, 1.6g/cm3 and 1.7g/cm3 respectively. The CU test of the saturated remolded loess at a confining pressure of 100kPa, 150kPa, and 200kPa was performed at a shear rate of 0.04mm/min, 0.08mm/min, 0.16 mm/min, and 0.4mm/min respectively. It is found that the stress-strain curve of saturated remolded loess gradually moves up with the increase of dry density. When the dry density is equal to ρd=1.5g/cm3, the deviatoric stress under different confining pressures there is a tendency to increase first and then decrease with increases of shear rate. When the dry density is equal to ρd=1.6g/cm3 and ρd=1.7g/cm3, the deviational stress under different confining pressures shows the trend of increasing first, decreasing and then increasing with the increase of shear rate, which is different from that at the dry density ρd =1.5g/cm3 at a shear rate v=0.4mm/min. When the dry density ρd=1.5g/cm3, the cohesive force decreases first and then increases with the increase of shear rate. When the dry density ρd=1.6g/cm3 and ρd=1.7g/cm3, the cohesive force first increases at 0.08 mm/min, and then decreases with the increase of shear rate. The cohesion and internal friction angles tend to increase as the dry density increases.

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Bulk modulus dispersion and attenuation in sandstones

Geophysics ◽

10.1190/geo2014-0335.1 ◽

2015 ◽

Vol 80 (2) ◽

pp. D111-D127 ◽

Cited By ~ 82

Author(s):

L. Pimienta ◽

J. Fortin ◽

Y. Guéguen

Keyword(s):

Fluid Flow ◽

Bulk Modulus ◽

Low Frequency ◽

Confining Pressure ◽

S Wave ◽

Standard Samples ◽

Stress Strain ◽

Fontainebleau Sandstone ◽

Attenuation Characteristic ◽

Confining Pressures

We report experimental data on the frequency dependence of bulk elastic modulus in porous sandstones. A new methodology was developed to investigate the dispersion/attenuation phenomena on a rock’s bulk modulus [Formula: see text] for varying confining pressures in the range of 1–50 MPa and fluids of varying viscosities (i.e., air, glycerin, and water). This methodology combined (1) ultrasonic (i.e., [Formula: see text]) P- and S-wave velocity measurements, leading to the high-frequency (HF) [Formula: see text], (2) stress-strain measurements from forced periodic oscillations of confining pressure at low-frequency (LF) ranges (i.e., [Formula: see text]), leading to [Formula: see text] and [Formula: see text], and (3) pore-pressure measurement to document the induced fluid-flow in the LF range (i.e., [Formula: see text]). The stress-strain method was first checked using three standard samples: glass, gypsum, and Plexiglas samples. Over the frequency and pressure range of the apparatus [Formula: see text] was stable and accurate and the lowest measurable LF attenuation was [Formula: see text]. The methodology was applied to investigate Fontainebleau sandstone samples of 7% and 9% porosity. The [Formula: see text] and [Formula: see text] exhibited correlated variations, which also correlated with an experimental evidence of frequency-dependent fluid-flow out of the sample. Attenuation peaks as high as [Formula: see text] and [Formula: see text] are measured. The attenuation/dispersion measured under glycerin saturation was compared to Biot-Gassmann predictions. The overall behavior of one sample was consistent with a dispersion/attenuation characteristic of the drained/undrained transition. On the reverse, the other sample exhibited exotic behaviors as the measurements were underestimated by the drained/undrained transition and indicated a direct transition from drained to unrelaxed domain. These different behaviors were consistent with the values of the critical frequencies expected for the drained/undrained (i.e., [Formula: see text]) and relaxed/unrelaxed (i.e., [Formula: see text]) transitions.

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True-Triaxial Drained Test of Tengger Desert Sand

Advances in Civil Engineering ◽

10.1155/2020/8851165 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Xuefeng Li ◽

Zhigang Ma ◽

Wennan Lu ◽

Yandong Wang

Keyword(s):

Confining Pressure ◽

Western China ◽

Test Results ◽

Tengger Desert ◽

Stress Strain ◽

True Triaxial ◽

Dense Sand ◽

Desert Sand ◽

Confining Pressures ◽

Triaxial Drained Test

For the lack of accurate test results in design and maintenance of desert-crossing highways in the Tengger Desert of western China, the GDS true-triaxial system was used to conduct the drained test on dense sand. Under the condition of different intermediate principal stress ratio b-value, the results showed that the stress-strain relationships in three orthogonal directions had significant differences, presenting significant anisotropy. The peak of the generalized shear stress increased with the increase of b-value. Except under the condition of b = 0, the specimen contracted firstly and then dilated, while the others dilated. The results of the different confining pressures showed that the stress-strain relationships appeared as a hardening type at low confining pressures, and as the confining pressure increased, the stress-strain relationships exhibit hardening, peaking, softening, and stable deformation characteristics. At low confining pressure, the contractive behaviors were not obvious, mainly as dilatancy, and as the confining pressure increased, the dilatancy increased gradually. The specimen transformed contract to dilatancy, and when the confining pressure reached 800 kPa, the specimen exhibited contractive behavior. The test results will provide data for subgrade design and construction in desert area.

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Mechanical Performance of Jute Fiber-Reinforced Micaceous Clay Composites Treated with Ground-Granulated Blast-Furnace Slag

Materials ◽

10.3390/ma12040576 ◽

2019 ◽

Vol 12 (4) ◽

pp. 576 ◽

Cited By ~ 12

Author(s):

Jiahe Zhang ◽

Amin Soltani ◽

An Deng ◽

Mark Jaksa

Keyword(s):

Blast Furnace ◽

Blast Furnace Slag ◽

Total Mass ◽

Mechanical Performance ◽

Strength Criterion ◽

Engineering Properties ◽

Granulated Blast Furnace Slag ◽

Multivariable Regression ◽

Strength And Stiffness ◽

Furnace Slag

The combined capacity of Jute Fibers (JF), the reinforcement, and Ground-Granulated Blast-Furnace Slag (GBFS), the binder, was examined as a sustainable solution towards ameliorating the inferior engineering properties of micaceous clays. A total of sixteen JF + GBFS mix designs, i.e., JF (% by total mass) = {0, 0.5, 1.0, 1.5} and GBFS (% by total mass) = {0, 3, 6, 9}, were tested for unconfined compression (UC) strength; for those mix designs containing GBFS, curing was allowed for 7 and 28 days prior to testing. Scanning electron microscopy (SEM) studies were also carried out to observe the evolution of fabric in response to JF, GBFS and JF + GBFS amendments. The greater the JF content the higher the developed strength and stiffness up to 1% JF, beyond of which the effect of JF-reinforcement led to some adverse results. The JF inclusions, however, consistently improved the ductility and toughness of the composite. The addition of GBFS to the JF-reinforced samples improved the soil–fiber connection interface, and thus led to further improvements in the composite’s strength, stiffness and toughness. The mix design “1% JF + 9% GBFS” managed to satisfy ASTM’s strength criterion and hence was deemed as the optimum choice in this investigation. Finally, a non-linear, multivariable regression model was developed and validated to quantify the peak UC strength as a function of the composite’s index properties. The proposed model contained a limited number of fitting parameters, all of which can be calibrated by little experimental effort, and thus implemented for preliminary design assessments.

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Compressive Strength of Mortar with Partial Replacement of Cement by Fly Ash and GGBFS.

Diyala Journal of Engineering Sciences ◽

10.24237/djes.2021.14412 ◽

2021 ◽

Vol 14 (4) ◽

pp. 146-155

Author(s):

Safie Safie Mahdi Oleiwi

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Construction Industry ◽

Optimal Level ◽

Partial Substitution ◽

Partial Replacement ◽

Curing Time ◽

Granulated Blast Furnace Slag ◽

Strength Tests ◽

Furnace Slag

The compressive strength characteristics of mortar containing Ground Granulated Blast Furnace Slag (GGBFS) and Fly Ash (FA) in mortar by partial substitution of cement are investigated in this work. The increased demand for cement in the construction industry is a concern for environmental degradation; in this case, waste materials such as GGBFS and FA are used to replace cement. The optimal level of GGBFS and FA was determined using a percentage range of 0% to 40% for different curing days. Compressive strength tests were performed on the replaced mortar. For all mixes, the binder-to-water ratio was kept at 0.4. The compressive strength tests were conducted for 7, 28 and 90 days of curing on a Mortar. The result obtained that as the curing time increased the compressive strength of mortar containing GGBFS and FA increased. In comparison to M1 (cement only), the compressive strength improved by 13.15 percent and 15.5 percent at M3 (20%FA) and M8 (30%GGBFS), respectively. The results showed that adding GGBFS and FA to mortar improve compressive strength, which is improves the mechanical properties of the mortar.

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