Shrinkage property of bentonite-sand mixtures as influenced by sand content and water salinity

Tan, Yu; Zhu, Fei; He, Dongjin; Zhu, Jiaoqun

doi:10.1016/j.conbuildmat.2019.07.051

Cited by 43 publications

(14 citation statements)

References 66 publications

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“…After being saturated with 2.0 mol/L CaCl 2 solution, the bentonite specimen, as shown in Figure 4(d), exhibits an apparent aggregate structure with complete disappearance of flat-shaped stacks of clay platelets, and the aggregated particles are arranged in a disordered manner with the presence of some interaggregate pores. e observed flocculation of clay particles induced by the saline solution is in reasonable agreement with existing studies [30,31]. It is of note that the particle aggregation for specimen 2.0Ca-T is more significant than that of specimen 2.0Na-T.…”

Section: Effect Of Salinization On the Microstructure Of Bentonitesupporting

confidence: 91%

Effects of Saline Solutions on the Desiccation Cracking and Shrinkage Behavior of Gaomiaozi Bentonite

Tan

Zheng

Liu

2020

Advances in Civil Engineering

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Bentonite, when used as buffer/backfill material in the deep disposal of high-level radioactive waste (HLW), could undergo desiccation shrinkage or even cracking due to the heat released from HLW, impairing the efficiency of the barrier system. Furthermore, in-service buffer materials are inevitably in contact with the groundwater, which sometimes contain high salt concentrations. The groundwater salinity may modify the properties of bentonite and hence affect the process of desiccation and its performance. To investigate this effect, in this study, a series of temperature-controlled desiccation tests was conducted on compacted specimens of Gaomiaozi (GMZ) bentonite preliminarily saturated with two different saline solutions (NaCl and CaCl2) at the concentration varying from 0.5 to 2.0 mol/L. The experimental results indicated that, as the concentration of saline solution increases, the initial saturated water content of bentonite decreases, whereas the residual water content at the completion of the desiccation test increases. The water evaporation rate is reduced for the specimens saturated with a high-concentration saline solution, and CaCl2 has a more significant influence on water evaporation than NaCl. The evolution of cracks on the sample surface during the desiccation process can be divided into four stages: crack growth, maintenance, closure, and stabilization; an increase in the salt concentration effectively inhibits crack development. It was shown that the infiltration of saline solutions alters the microstructure of bentonite by changing the arrangement of clay particles from a dispersed pattern to more aggregate state, which results in a decrease in shrinkage strain and shrinkage anisotropy.

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Section: Effect Of Salinization On the Microstructure Of Bentonitesupporting

confidence: 91%

Effects of Saline Solutions on the Desiccation Cracking and Shrinkage Behavior of Gaomiaozi Bentonite

Tan

Zheng

Liu

2020

Advances in Civil Engineering

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“…Available length scales of M40, M60, M80, and M100 were 0.370-5.543, 0.280-3.917, 0.227-3.181, and 0.185-2.768 ms, respectively. After the slopes of the curves were determined, the fractal dimensions were determined by Equation (11). The fractal dimensions of the eight mixtures are shown in Figure 13.…”

Section: Determination Methods Of T2c Based On Fractal Analysismentioning

confidence: 99%

“…Many studies have shown that adding quartz to clay can solve this problem. The addition of quartz can reduce the water sensitivity and enhance the strength of clay while maintaining a low permeability coefficient [9][10][11]. Clay-quartz mixtures are suitable materials for building barriers of waste landfill sites.…”

Section: Introductionmentioning

confidence: 99%

Permeability Evaluation of Clay-quartz Mixtures Based on Low-Field NMR and Fractal Analysis

Sha

Wang

2020

Applied Sciences

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Nuclear magnetic resonance (NMR) technology has been widely used for predicting permeability coefficients of porous medium, such as shales, sandstones, and coals. However, there have been limited studies on the prediction model of clay-quartz mixtures based on NMR technology. In this study, evaporation tests at 40 °C and NMR tests were simultaneously performed on eight clay-quartz mixtures with different mineral compositions. The results show that during the evaporation process, the decay rate of T2 total signal amplitudes was constant at first, and then decreased to 0 after a period of time. Based on the decay rate, the evaporation process was divided into two stages: the constant rate stage and the falling rate stage. Based on the two stages, the T2 cut-offs of eight mixtures were determined. The water in the mixture was divided into two parts by the T2 cut-off: the free water and the bound water. The prediction model of permeability coefficients of clay-quartz mixtures was established based on the Timur-Coates model. In order to simplify the process of predicting the permeability coefficient, fractal analysis was used to develop the relationship between the T2 cut-off and fractal dimension of the T2 spectrum of saturated mixture. A simplified method for predicting permeability coefficients of clay-quartz mixtures based on NMR technology without centrifugal and evaporation experiments was also proposed.

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“…is method is widely used for improving high plasticity soils, such as expansive soil and other fine-grained soils [13][14][15][16][17]. For this reason, some laboratory tests were completed to study the mechanical behavior of high plasticity soil improved by adding gravel [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…Guo et al [10] found that increasing sand content could considerably enhance the strength of high plasticity soil. Zhang et al [17] stated that when the sand content is more than 30%, the volume shrinkage rate can be reduced and the soil strength can be greatly increased. However, most of these studies went no further than the analysis of the physical and mechanical properties of improved high plasticity soils and gave little attention to the improvement mechanism.…”

Section: Introductionmentioning

confidence: 99%

Influence of Gradation on Resilient Modulus of High Plasticity Soil‐Gravel Mixture

Liu

Ren

Zhang

et al. 2020

Advances in Civil Engineering

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Because of low resilient modulus, high plasticity soil is often not allowed to fill road subgrades and is discarded as construction and demolition waste (CDW). To make use of the CDW, this study explored the possibility of improving high plasticity soil with gravel and examined the effect of gravel gradation on the resilient modulus of the soil-gravel mixture. A series of dynamic triaxial tests, tests of voids in coarse aggregate, and X-ray CT scans were carried out on high plasticity soil-gravel mixtures of different gravel contents and gravel gradation types. The test results show that there is a critical gravel content, that is, 44.1%. When the gravel content is less than 44.1%, the mixture shows a dense suspended structure and its modulus increases slowly with increasing gravel content. When the gravel content is greater than 44.1%, the mixture exhibits a dense skeleton structure and the modulus increases rapidly as the gravel content rises. Moreover, as the gravel gradation tends to the lower type, coarse aggregates increase in quantity and contact each other to form a dense skeleton; thus, the modulus increases accordingly. As the gravel gradation approaches the upper type, coarse aggregates decrease in quantity and tend to suspend in the soil, so the modulus decreases. With the increase in contact number, the skeleton structure is continuously improved, and thus the modulus is enhanced progressively. The results indicate that the gravel mixing method with a gravel content of 40%–45% can effectively improve high plasticity soil and shows great environmental and economic benefits.

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Shrinkage property of bentonite-sand mixtures as influenced by sand content and water salinity

Cited by 43 publications

References 66 publications

Effects of Saline Solutions on the Desiccation Cracking and Shrinkage Behavior of Gaomiaozi Bentonite

Effects of Saline Solutions on the Desiccation Cracking and Shrinkage Behavior of Gaomiaozi Bentonite

Permeability Evaluation of Clay-quartz Mixtures Based on Low-Field NMR and Fractal Analysis

Influence of Gradation on Resilient Modulus of High Plasticity Soil‐Gravel Mixture

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