Thickness Of Diffuse Double Layer Research Articles

Membrane behavior of clay under mixed solution conditions

Compacted clay is employed as the buffer material for landfills, and multiple ions are dissolved in the leachate restricted by the compacted clay layer. The membrane efficiency is an important indicator to assess the barrier properties of the compacted clay layer and is measured through membrane tests. However, most membrane tests are currently conducted with a single solute solution, which does not reflect the mixed solution characteristics of leachates. To assess the membrane efficiency of compacted clay under mixed solution conditions, 13 membrane tests were conducted on a bentonite-amended soil using KCl–NaCl mixed solutions, KCl–CaCl2 mixed solutions, and KCl–AlCl3 mixed solutions with different mixing ratios at a total concentration of 20 mM. Nuclear magnetic resonance (NMR) tests were conducted on the soil specimen after the membrane tests to investigate the micromechanism of the membrane behavior under mixed solution conditions. Results indicate that the membrane efficiency increased with the mixing ratio of Na+ but decreased with the mixing ratio of Ca2+ or Al3+. In the 13 membrane tests, the lowest membrane efficiency was achieved when the specimen was tested with pure AlCl3 solution. The relationship between the membrane efficiency and mixing ratio was also investigated at the microscopic scale. As the ion valence increases, the diffuse double layer thickness is smaller and the proportion of macropores is larger, as verified by NMR tests.

Determining Liquid Limit and Plastic Limit of Clay Soils by Electrical Surface Conduction and Diffuse Double Layer Thickness

The aim of this study was to propose a new approach to determine the liquid limit and plastic limit of clay soils by considering electrical conductivity (EC) measurements. The proposed method included incorporating a new parameter, F, which is the ratio of the volumetric water contents of diffuse double layer (DDL) water and free water. In addition, the EC parameter, σ, was considered as the ratio of electrical surface conductivity and electrical conductivity of water. The changes in the thickness of DDL (χ) were also assessed to obtain corresponding equations to establish a connection with clay mineralogy, water content, and specific gravity in the final prediction. Three-dimensional surface analyses were conducted to find a correlation among F, σ, and χ to identify an appropriate method to predict liquid limit and plastic limit. The study was conducted with 39 different types of samples, and the outcomes from the EC approach were validated against the conventional methods. Overall, the coefficient of determination, R2 = 0.90, and Lin’s concordance correlation coefficient, (LCCC) = 0.91, were obtained for liquid limit prediction, whereas R2 = 0.64 and LCCC = 0.80 were obtained for plastic limit determination.

Incorporating potassium-rich waste material in a sustainable way to stabilize dispersive clay: A novel practical approach for the construction industry

The inappropriate use of dispersive clay in constructing roads/highways, embankments, and other structures causes significant challenges to the construction industry. The dispersive clay treatment in this work was carried out for the first time using eco-friendly and sustainable potassium-based material rather than calcium-based, which makes it particularly innovative. This study investigated the impact of potassium-rich wood ash (KRWA) on dispersion, index, unconfined compression strength (UCS), consolidation, physio-chemical, mineralogical and microstructure properties. KRWA amount varied up to 35% and cured for up to 60 days at about 20 to 25 °C. The results revealed that 10% KRWA is the optimum content, decreasing the dispersion and sodium percentage by 82% and 57%, respectively, with 28 days of curing and changing the soil class to non-dispersive. A 56% reduction in plasticity was observed with optimum content, which caused the soil to become more friable, enhancing the treated clay's workability. Moreover, a 575% raise in UCS and a 60% reduction in compressibility were witnessed, which indicates improved load-bearing capacity and the capability of the stabilized clay to bear external loads better. The physio-chemical study revealed that the ion exchange, agglomeration, and flocculation take place immediately with minor/no curing that decreased the repulsion and diffuse double layer thickness, followed by the initiation of the pozzolanic activity, which formed different cementitious gels. X-ray diffraction and scanning electron microscopy experiments confirmed the formation of gels and produced a considerably thicker microstructure. Moreover, cost-based analysis shows that KRWA is more economical than conventional additives for highway/road applications.

Reliability of chemical osmosis as a practical method to extract water out of shale and promote shale’s mechanical stability

Wellbore instability in shale formations is one of the most bothersome problems leading to significant changes in shale’s petrophysical, mechanical, and chemical properties, and could cost billions of dollars annually. Drilling fluid’s ionic composition is one of the factors affecting wellbore stability. This paper investigates the impact of chemical osmosis, ionic diffusion, and diffusion osmosis on the stability of shale, identify the critical salt concentration, and examine the impact of ionic type and concentration on shale stability. Experimental methods include utilization of shale I and II through linear expansion and gravimetric measurement tests using different salts. Results show that the critical salt concentration in shale I and II is 8 w/w%. Chemical osmosis is found to be a reliable method for water extraction out of shale if critical concentration value is not surpassed. Beyond this value, the ionic diffusion and diffusion osmosis in shale I and II were adversely affecting shale’s mechanical and chemical stability. The swelling and gravimetric ions and water uptake tests showed that shale is a leaky semi-permeable membrane, and that chemical osmosis could be jeopardized by ionic transport into shale. However, the water transport impact on changes in the thickness of diffuse double layer of clay needs to be investigated. The impact of temperature on water and ions transportation into shale needs to be examined to reflect in-situ conditions. In this study, the cation type that makes up the salt was varied while the anion type was fixed. Since both cations and anions tend to diffuse into shale in the presence of a concentration gradient, it is recommended to vary the anion type to study the combined impact of cation and anion type on shale stability.

Compressibility Behavior of Bentonites by Stern Theory based on Constant Surface Charge Conditions

AbstractThe compressibility behavior of clays is governed by the electrical double layer formed around the clay particles. The Gouy-Chapman diffuse double layer theory is often utilized to predict the compressibility behavior of clay minerals. The theory does not consider the effect of the size of the cations, however, and thus predicts unrealistically small void ratios for compacted bentonites under large mechanical pressures expected in high-level nuclear waste-repository applications. In this study, the Stern layer was introduced to incorporate the cation size effect in the prediction of the compressibility behavior of bentonites. The overall diffuse double-layer thickness at large pressures was much smaller than the initially assumed Stern layer thickness based on the exchangeable cation size for all the bentonites studied. A compressible Stern layer was, therefore, considered for the first time in the prediction of the compressibility behavior of bentonites. The compression behavior of the Stern layer under the applied loading is influenced by the ratio of the mid-plane to the Stern potential, which is dependent on the type and composition of the exchangeable cations on the clay surface. Stern layer compression was initiated when the potential ratio was in the range 0.65–0.75 for bentonites with various surface cation characteristics. The incorporation of cation size and a compressible Stern layer provided significant improvements over the existing models in predicting the compressibility behavior of bentonites over a wide pressure range. The compressibility data predicted by the proposed model showed very good agreement with the data measured for five bentonites from the literature in the pressure range 0.1–42 MPa.

Effect of water chemistry on the hydro-mechanical behaviour of compacted mixtures of claystone and Na/Ca-bentonites for deep geological repositories

In the French deep geological disposal for radioactive wastes, compacted bentonite/claystone mixtures have been considered as possible sealing materials. After emplacement in place, such mixtures are hydrated by the site solution as well as the cement solution produced by the degradation of concrete. In this study, the effects of synthetic site solution and cement solution on the hydro-mechanical behaviour of compacted mixtures of claystone and two types of bentonites (MX80 Na-bentonite and Sardinia Ca-bentonite) were investigated by carrying out a series of swelling pressure, hydraulic conductivity and mercury intrusion porosimetry (MIP) tests. It was found that for the MX80 bentonite/claystone mixture hydrated with synthetic site solution, the swelling capacity was reduced compared to the case with deionised water owing to the transformation of Na-montmorillonite to multi-cation dominant montmorillonite by cation exchanges. For the Sardinia bentonite/claystone mixture, the similar increasing rate of swelling pressure was observed during the crystalline swelling process for different solutions, suggesting insignificant cation exchanges. Additionally, the cations in the synthetic site solution could reduce the thickness of diffuse double layer and the osmotic swelling for both MX80 bentonite/claystone and Sardinia bentonite/claystone mixtures. The large-pore volume increased consequently and enhanced water flow. In the cement solution, the hydroxide could also dissolve the montmorillonite, reducing the swelling pressure, and increase the large-pore volume, facilitating the water flow. Furthermore, the decrease of swelling pressure and the increase of hydraulic conductivity were more significant in the case of low dry density because of more intensive interaction between montmorillonite and hydroxide due to the high permeability.

Effects of microbially induced carbonate precipitation on diffuse double layer and particle fabric of oil sands fine tailings

Microbially induced carbonate precipitation (MICP) is a sustainable biological process that catalyzes carbonate mineral precipitation within geomaterials. This study evaluates the performance and mechanisms of the MICP treatment for flocculating the oil sands fine tailings (FT). Column tests showed that the untreated FT did not decant during the 31 days. However, the MICP technique shortened the dewatering process. To elucidate the mechanisms of the MICP-induced flocculation of the FT, the diffuse double layer (DDL) thickness and microstructure of the specimens were evaluated. Three chemical equilibrium scenarios that gradually considered the MICP-biochemical reactions were explored to analyze the change of the DDL thickness. The results showed that increasing of ionic strength by urea hydrolysis decreased the DDL thickness. The fabric observation indicated that the specimens with the most calcium carbonate precipitation had the densest fabric. In summary, the MICP technique densified the fabric of FT via the ureolysis process and precipitating minerals.

Insight into Debye H\xfcckel length (\u03ba\u22121): smart gravimetric and swelling techniques reveals discrepancy of diffuse double layer theory at high ionic concentrations

Smart gravimetric and swelling techniques were utilized in this work to examine the validity of the Debye Hückel length (κ−1) equation when shale interacts with highly concentrated salt solutions. The swelling and shrinkage behavior of two different shales, when exposed to monovalent and divalent ionic solutions (NaCl, KCl and CaCl2) at concentrations ranging from 2 to 22%w/w was observed and measured. Shale swelling and shrinkage results show that Debye Hückel length (κ−1) equation seems to work adequately at low ionic concentrations where osmotic water flow out of shale plays a major role in decreasing the diffuse double layer thickness by withdrawing water out and thereby shrinking κ−1. At high ionic concentration levels, the flow of associated water into the diffuse double layer negates the withdrawal of osmotic water out of the diffuse double layer which could maintain κ−1 or possibly increase it. Data on measured ionic uptake into shale suggests that excessive ionic diffusion into shale, especially at high concentrations, leads to higher electrical repulsion between alike ions in the diffuse layer which could lead to the expansion of the diffuse double layer thickness. Furthermore, swelling and shrinkage data analysis for shale suggests the existence of a ‘critical concentration’ below which the Debye Hückel length equation works. Above the critical concentration, the validity of the Debye Hückel length equation might be in question. The critical concentration is different for all ions and depends on ionic valence, hydrated ion diameter, and clay type.

Improving the mechanical behaviour of clay contaminated with glycerol and anthracene using lime and Portland cement

ABSTRACT The specimens of contaminated clay improved with Portland cement and lime were cured for seven days and were subjected to uniaxial compressive strength (UCS) testing. The results for anthracene-contaminated specimens improved with three percent Portland cement (by weight of clay) were approximately equivalent to those improved with 10% lime. The results for glycerol-contaminated specimens improved with nine percent Portland cement was approximately equivalent to that improved with 10% lime. According to the results, both Portland cement and lime were able to improve the clay soil contaminated with anthracene and glycerol, but Portland cement had a greater effect than lime on the anthracene-contaminated specimens because of the non-polar behaviour of anthracene and the grain-like (flocculated) behaviour of the contaminated soil. These factors were the result of a decrease in the diffuse double layer thickness by anthracene, which has a lower dielectric constant relative to water. The lime had a greater effect than cement on the specimens contaminated with glycerol because of the polar behaviour of glycerol, the increase in the required moisture content for hydration, and because the dielectric constant of glycerol is close to that of water. These results were evaluated and confirmed by scanning electron microscopy.

Long-term effect of water chemistry on the swelling pressure and hydraulic conductivity of compacted claystone/bentonite mixture with technological gaps

A compacted mixture of Callovo-Oxfordian (COx) claystone/MX80 bentonite is a promising sealing material in the French Cigéo project for radioactive waste disposal at great depth. Over time, the sealing material will be saturated by the site water originating from the surrounding rock and the water chemistry can affect the performance of the sealing material. In this study, the effects of water chemistry and technological gaps on the hydro-mechanical property were investigated by performing hydration tests on the compacted claystone/bentonite mixture with technological gaps using deionised water and synthetic site solution for 10 and 590 days. After the tests, the dry density, water content and microstructure distributions were also determined to complement the program. Results show that the synthetic site solution did not affect the swelling pressure and hydraulic conductivity after a short term of 10 days. With the increase of hydration time, the specimens with technological gaps tended to be homogeneous, resulting in a reduction of hydraulic conductivity. Because of the cation exchanges and the decreased diffuse double layer thickness, the synthetic site solution reduced the swelling pressure and increased the hydraulic conductivity in long term, especially for the specimens with lower global dry densities.

Insight on the inhibitive property of potassium ion on the stability of shale: a diffuse double-layer thickness (\u03ba\u22121) perspective

It is believed that potassium ions reduce the hydration energy and swelling of clays and thus promoting stability to shales. This belief was made based on volumetric and linear expansion data obtained from shale and KCl solutions interactions. However, swelling data alone is not adequate to mitigate wellbore instability in shale. Such data must be incorporated with mechanical and physicochemical data for complete and accurate wellbore instability analysis.This paper presents clear experimental evidence showing that concentrated potassium chloride solutions tend to suppress shale swelling as higher concentration of potassium ions collapses the diffuse double layer of clay particles causing shale shrinkage which confirms the notion that the Debye length (κ−1) decreases as the ionic concentration increases.Results show that there exists a KCl concentration threshold above which shale’s compressive strength deteriorates significantly. This concentration threshold was found to hover around 5% by weight. The amount of water and ions uptake into shale was quantified using gravimetric measurements. Significant potassium ions invasion into shale was experimentally measured as KCl solution concentration increased which proved the leaky nature of shale’s membrane. The reduction of shale’s compressive strength seems to be well correlated with the amount of ions uptake into shale. Moreover, data suggests that shale’s compressive strength was not significantly impacted by swelling. It was possible to gravimetrically separate osmotic water from associated water as shale interacted with KCl solutions. Results suggest that osmotic water is responsible for shale swelling since it is unattached to ions which makes it free to move around inside shale. On the other hand, data suggest that associated water does not contribute to shale swelling as it is bound to potassium ions which makes it unfree to move around. It is fair to state, based on our experimental data, that osmotic water is responsible for shale swelling while associated water contributes to shale’s compressive strength alteration.

Macrostructural and Microstructural Properties of Residual Soils as Engineered Landfill Liner Materials

ABSTRACT This study assessed the performance of residual soils with regard to their macrostructural and microstructural properties and compatibility with leachate in pursuit of exploring alternative cost-effective and efficient landfill liner materials. A series of laboratory investigations was conducted on three residual soil samples by using tap water and leachate as permeation fluid to achieve the objectives of the study. The zeta potential measurements revealed that the presence of multivalent cations in the leachate decreased the diffuse double layer (DDL) thickness around the soil particles. The reduced DDL thickness caused a decrease in Atterberg limits of soil-leachate samples and changes in the classification of fine fractions. Additionally, the effects of pore clogging attributed to chemical precipitation and bioclogging were responsible for the reduction in measured hydraulic conductivities of soil-leachate samples. These effects can be clearly observed from the field-emission scanning electron microscopy images of soil-leachate samples with the appearance of less visible voids that led to a more compact and dense structure. The formation of new non-clay minerals and associated changes in the Al and Si ratio as reflected in the x-ray diffraction diffractograms and energy-dispersive x-ray analyses, respectively, were attributed to the effects of chemical precipitation. This study concluded that S1 and S2 residual soil samples are potential landfill liner materials because they possess adequate grading characteristics, adequate unconfined compressive strength, low hydraulic conductivity, and good compatibility with leachate. In contrast, the S3 sample requires further treatment to enhance its properties in order to comply with the requirements of landfill liner materials.

Justification of strength properties of microstructural changes in the black cotton soil stabilized with rice husk ash and carbide lime in the presence of sodium salts

Black cotton soils exhibit high shrinkage and swelling characteristics due to the variation in moisture content. To overcome this problem, many techniques are adopted, among which is the soil stabilization technique. Rapid industrialization and urbanization lead to the generation of waste products; the major by-products are rice husk ash (RHA) and carbide lime (CL). These by-products show excellent pozzolanic property. In this paper, an attempt has been made to stabilize black cotton soil with rice husk ash (RHA) along with carbide lime (CL) and other additives. Based on strength test results, the optimum dosage of RHA and CL was found to be 20% and 8%, respectively. The effect of sodium salts on index properties and unconfined compression strength (UCC) test at different moulding water contents for immediate testing and at different days of curing are studied. Results show that plasticity index of the soil treated with additives was decreased both for immediate and for 7 days of curing period due to the decrease in diffuse double-layer thickness. Soil–RHA–CL composite treated with 1% sodium chloride and 1% sodium hydroxide improves the Unconfined compression strength and shows a better strength compared to carbide lime-treated soil due to the formation of alkali silicate and alkali aluminate hydrated gel along with other cementitious products. The microstructural changes in the stabilized composite can be observed with XRD and SEM analysis. The addition of carbide lime and salts binds the particle with hydrated gel and shows denser environment compared to unstabilized soil.

Geotechnical characterization and collapsibility of a natural dispersive loess

During preliminary investigation phase of the national Chabahar-Zahedan railway line, serious geotechnical problems including non-uniform settlements, tensile cracks, and local collapse were reported in parts of the path near the coastline. A follow-up field investigation revealed that the in-situ soil at construction site has a metastable structure being sensitive to saturation and loading. Therefore, a comprehensive series of physical, chemical, electro-chemical, and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state. The natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics. Given its significant collapse potential, the soil was assigned into the category with “severe trouble” for construction purposes. Importantly, our tests revealed that a threefold reduction in pore water salinity results in >4% rise in collapse potential of similar specimens. Reduction in salt concentration increases the thickness of diffuse double layer and hence collapsibility. In addition, strain softening shear behavior was observed for elevated confining stresses under undrained triaxial stress state. In fact, this brittle type failure mechanism associated with continuous generation of pore water pressure is undesirable as catastrophic failures could happen with no advance warning.

Absence of diffuse double layer effect on the vibrational properties and oxidation of chemisorbed carbon monoxide on a Pt(111) electrode

In this work we investigate the effects of the diffuse double layer thickness on the electrochemical Stark tuning and oxidation of carbon monoxide at Pt(111) surfaces in perchloric acid solution. The diffuse double layer thickness was modified by changing the concentration (ionic strength) of the supporting electrolyte. The Stark tuning slope of the adsorbed CO was evaluated with Fourier Transformed Infrared Spectroscopy, and the CO oxidation was monitored with cyclic voltammetry. The results show that both electrochemical Stark tuning and oxidation are independent of the HClO4 concentration of the supporting electrolyte, revealing the absence of diffuse layer effects on the aqueous Pt(111)/CO system. By comparison to previously reported theoretical calculations, we attribute this insensitivity to the special double layer structure of Pt(111)/CO, in which the potential drop occurs primarily between the terminating oxygen of the adsorbed CO adlayer and first water layer of the electrolyte, making the properties of adsorbed CO nearly independent of the ionic strength of the electrolyte.

Investigation of Liner Systems in Transport of Organic and Inorganic Contaminants in Sanitary Landfill: A Case Study

In the present work, a pilot‐scale study was carried out to investigate the diffusive transport of phenolic compounds and advective transport of heavy metals through liner systems composed of alternative materials and to evaluate the leachate effect on liner materials’ properties. For this purpose, ten pilot‐scale landfill reactors were operated for a period of about 290 days. Physico‐chemical, mineralogical composition, and geotechnical properties of liner materials were also reported. The results of the study suggest that performance of alternative liner systems have no significant difference in toxic organic contaminant attenuation and clay‐lime mixture were found to be the less effected liner system by leachate. Thereby clay‐lime mixtures can be effectively utilized as a component of landfill liners due to not only chemical, physical, and mineralogical properties but also their high abundance and low cost supply. A two‐layer liner system composed of clay‐lime mixture at the upper part and bentonite‐zeolite mixture at the lower part is recommended. Existence of lime at the upper part will provide improvement in soil properties and reduce leachate effects but will increase hydraulic conductivity by decreasing the thickness of diffuse double layer. A bentonite‐zeolite mixture existing at the lower part will provide adsorption of heavy metals and avoid heavy metal migration.

Effect of pore fluid osmotic suction on matric and total suctions of compacted clay

The experimental results of the present study on compacted expansive clay illustrate that matric suction increases with the increase in pore fluid osmotic suction due to changes in soil structure. Scanning electron micrographs show that particle stacking (aggregations) increases with increase in pore fluid osmotic suction and cation valence due to reduction in diffuse double layer thickness, and thus results in a reduction in micro pore size with a corresponding increase in macro pore size. At a given water content, the macro pore degree of saturation reduces with the increase in osmotic suction owing to the increase in macro pore size and leads to an increase in matric suction, as the matric suction is characteristic of the macro pore and the degree of saturation of the macro pore. The matric, osmotic and total suction measurements using the filter paper method also confirm that the matric and osmotic suction components are additive. This demonstrates that the method of obtaining matric suction from the difference between total suction and pore fluid osmotic suction determined using non-contact filter papers is reliable.

Infiltration of Pb(II) solution in compacted bentonite/sand mixture under unconfined conditions

Compacted mixture of bentonite and sand has been proposed for using as buffer/backfill material in the disposal of high-level radioactive waste in many countries. The hydraulic behaviors and deformation properties of this material can be influenced by the chemical composition of groundwater. In the present work, the infiltration test of Pb(II) solution was conducted on compacted Gaomiaozi (GMZ) bentonite/sand mixture under unconfined conditions. The moisture migration characteristics and swelling properties were analyzed. Results show that the moisture migrates more quickly in the GMZ bentonite/sand mixture infiltrated with Pb(II) solutions than that in the pure GMZ bentonite hydrated with pure water for a same bentonite dry density. This difference could be explained by the chemical influence of Pb(II) on the thickness of diffuse double layer. For the bentonite/sand mixture with high bentonite content, its hydraulic conductivity depends on the bentonite dry density, regardless of the influence of the sand content. The hydration rate of the specimen is a function of the infiltration time and the distance from the wetting end. The largest swelling deformation was observed at the wetting end. At a given location, the vertical displacement was larger than any unilateral one of both sides. After the infiltration test, the inductively coupled plasma emission spectrometer, mercury intrusion porosimetry, and environmental scanning electron microscope tests were conducted for investigation of the Pb(II) distribution and microstructural characteristics of the tested specimen. Results show that, as the distance from the wetting end increases, the Pb(II) content nonlinearly decreases from 4.48 to 0.07 mg/g while the micro-pore increases and the macro-pore decreases.

Removal of Suspended Colloids through the Control of Their Zeta Potential

The effect of CaO, Na2SiO3, Al(OH)3, Al2(SO4)3, and CaCl2 on the surface charge and the diffuse double layer (DDL) thickness of a natural tropical peat were investigated in this study. Consequently, the flocculation and coagulation behavior of peat colloids were studied. As result, the thickness of DDL were changed significantly due to the addition of each electrolytes. The compression of the DDL thickness causes a weaker electrostatic repulsion and therefore a higher settlement rate. The surface charge of pure peat was almost zero at pH 3.2. The pH at the isoelectric point was increased by increasing the electrolyte concentration. The resulted flocculation and coagulation behavior of suspended peat in cationic reagents was in contrary with the surface electrical charge characteristics where the Na2SiO3 and the Al2(SO4)3 electrolytes showed the lowest and highest settlement rate, respectively.

Influence of Infiltration of Sodium Chloride Solutions on SWCC of Compacted Bentonite–Sand Specimens

The degree of saturation of compacted bentonite buffer in deep geological repositories is subject to alterations from infiltration of groundwater and heat emanated from the waste canisters. The matric suction (ψ)–degree of saturation (S r ) relations of unsaturated clays is represented by soil–water characteristics curves (SWCC) that are influenced by soil structure, initial compaction condition and stress history. Infiltration of groundwater besides increasing the degree of saturation can also alter the pore water chemistry; the associated changes in cation hydration and diffuse double layer thickness could impact the micro-structure and matric suction values. This study examines the influence of infiltrating sodium chloride solutions (1,000–5,000 mg/L) on the transient ψ–S r relations of compacted bentonite–sand specimens. Analysis of the ψ–S r plots, and X-ray diffraction measurements indicated that infiltration of sodium chloride solutions has progressively less influence on the micro-structure and SWCC relations of bentonite–sand specimens compacted to increasingly higher dry densities. The micro-structure and SWCC relations of specimens compacted to 1.5 Mg/m3 were most affected, specimens compacted to 1.75 Mg/m3 were less affected, while specimens compacted to 2 Mg/m3 remained unaffected upon infiltration with sodium chloride solutions.