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Water-repellent soils have a potential as alternative construction materials that will improve conventional geotechnical structures. In this study, the potential of chemically treated water-repellent kaolin clay as a landfill cover material is explored by examining its characteristics including hydraulic and mechanical properties. In order to provi...
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Context 1
... kaolin was thoroughly washed several times with deionized water to remove any contaminants and then dried in an oven (Hyundae Precision Industry, Seoul, Korea) for 24 h. 3 kg of the dried soil was mechanically blended with deionized water (6 L) for 24 h to ensure complete dispersion. In order to assign different degrees of water repellency, six different concentrations (CO) of Zycosoil (WZycosoil/Wwater = 0.5%, 0.75%, 1%, 2.5%, 5%, and 10%) were poured into the slurry (Table 2). After continuous stirring for 24 h, the treated clay was washed several times with deionized water to remove surplus organosilane and then dried in an oven for 24 h. ...
Context 2
... kaolin was thoroughly washed several times with deionized water to remove any contaminants and then dried in an oven (Hyundae Precision Industry, Seoul, Korea) for 24 h. 3 kg of the dried soil was mechanically blended with deionized water (6 L) for 24 h to ensure complete dispersion. In order to assign different degrees of water repellency, six different concentrations (CO) of Zycosoil (WZycosoil/Wwater = 0.5%, 0.75%, 1%, 2.5%, 5%, and 10%) were poured into the slurry (Table 2). After continuous stirring for 24 h, the treated clay was washed several times with deionized water to remove surplus organosilane and then dried in an oven for 24 h. ...
Context 3
... kaolin was thoroughly washed several times with deionized water to remove any contaminants and then dried in an oven (Hyundae Precision Industry, Seoul, Korea) for 24 h. 3 kg of the dried soil was mechanically blended with deionized water (6 L) for 24 h to ensure complete dispersion. In order to assign different degrees of water repellency, six different concentrations (C O ) of Zycosoil (W Zycosoil /W water = 0.5%, 0.75%, 1%, 2.5%, 5%, and 10%) were poured into the slurry (Table 2). After continuous stirring for 24 h, the treated clay was washed several times with deionized water to remove surplus organosilane and then dried in an oven for 24 h. ...
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Citations
... Synthetic substances like wax coatings, Tung Oil, Paraffin Oils, and Silanes have been used to engineer water repellency in soils (Bardet, Jesmani, and Jabbari 2014;Chan and Lourenço 2016;Ng and Lourenço 2016). Silanes and siloxanes, in particular, are very effective in making soils hydrophobic, with studies showing that adding 2.5% or less by mass can induce water repellency (Brooks et al. 2022;Choi et al. 2016;Uduebor et al. 2022). An accurate assessment of the effectiveness of various treatment methods for inducing soil water repellency is essential. ...
... Advancements have been made to ensure repeatability, including testing uniform-grained samples (Y. Choi et al. 2016), employing semi-automated techniques (Saulick, Lourenço, and Baudet 2017), and automating the test procedure using defined drop volumes, height, and plane thickness (Feyyisa, Daniels, and Pando 2017). ...
... For aspects of the tests where sieving was required, the soils were passed through a set of sieves (#10, #16, #20, #40, #60, #80, #100, #160, #200) and the mass retained on each sieve, stored separately for testing (Figure 7). Studies have asserted that fairly uniform soil grains for the test make for a better, repeatable test (Choi et al. 2016). ...
Moisture-related pavement distresses lead to significant damage and recurring maintenance costs with substantial CO 2 emissions. Engineering water repellency in pavement soils can help maintain uniform moisture conditions that improve and maintain performance, reduce design speculation, lowering material and construction costs, and emissions. This study examines the impact of grain size on water repellency treatment effectiveness. Soils from U.S. low volume roads and glass beads were treated with organosilane. Results showed effective water repellency, with contact angles ranging from 119.5° to 148.5°. Larger grain size reduced contact angle while increasing surface roughness raised it. Water drop penetration time tests showed no penetration after 2 hours (7200s), regardless of grain size, with breakthrough pressure values declining with larger grain and pore sizes (2kPa-0.1kPa). This study discusses highlights the importance of considering grain and pore size effects when using water-repellent soils in pavement construction.
... While both untreated and synthesised LBS had carbon, oxygen and silicon as their predominant constituents, their relative compositions differed: following synthesis with SHB, the carbon content of the particle increased from ~17% to a maximum of ~67%. Similar increases have also been observed by Choi et al. [11] following the synthesis of clay particles using Zycosoil, a commercially available chemical agent and by Wang et al. [12] after hydrophobising flat metallic substrates. In this study, the increase in carbon content is primarily attributed to the presence of the films and polymers. ...
The impact of hydrophobicity on unsaturated granular materials is important because suction is a function of the degree of saturation as well as the surface tension and contact angle of the water menisci. In this study, coatings have been applied on the surfaces of a quartzitic sand at different concentrations following synthesis with eight commercial chemical agents and dimethyldichlorosilane (DMDCS) to induce hydrophobicity. Contact angle (CA) measurements and water drop penetration time (WDPT) tests have been carried out at different time intervals to investigate the hydrophobicity and its persistence. Scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDS) was performed to evaluate the resulting chemical composition of the sand. Results demonstrate that synthesis at high concentration (5%) caused fluctuations in CA and WDPT measurements within the first 24h. Except for one commercial chemical agent, the maximum CAs reached by the remaining agents after 24h were comparable to DMDCS (CA=119°). However, the critical concentration needed to achieve these CAs differed significantly: the lowest critical concentration amongst the commercial chemical agents was 0.2% whereas with DMDCS, the critical concentration was 0.0053%. The resulting surface properties of the synthesised granular materials with the commercial chemical agents showed increases in carbon content whereas with DMDCS, no change was recorded compared to the untreated sand. In addition to illustrating the efficacy of commercial chemical agents in inducing hydrophobicity in granular materials, this study has provided insights into the timedependent hydrophobic behaviour of granular materials following synthesis.
... Zhao et al. [30] applied silicone materials for loess slope protection. Choi et al. [31] and Haquie et al. [32] used hydrophobic materials, such as organic silane, to improve the permeability of kaolin. The authors reported that organic silane changed the particle size distribution, enhanced the adhesion between particles, and reduced the water absorption. ...
This paper proposes the addition of an environmentally friendly silicone hydrophobic powder (SHP) to compacted loess to enhance its impermeability and reduce the settlement caused by wetting deformation. A flexible wall permeability test was conducted to examine the permeability coefficient of compacted loess with different dry densities mixed with different proportions of the SHP. Water drop infiltration testing, low-temperature drying testing, low-field nuclear magnetic resonance testing, and scanning electron microscopy were performed to clarify the occurrence state and permeability reduction mechanism of the SHP between loess particles from the microscopic viewpoint of the loess structure. The permeability coefficient of the compacted loess decreases significantly after adding 1–3% SHP. Specifically, the permeability coefficient of the loess with low compaction degree (1.35 g/cm3) decreases by 87% after the addition of 3% SHP. Moreover, the permeability coefficient of the loess with a compaction degree of 1.50 g/cm3 decreases from 1.58 × 10−6 to 7.9 × 10−8 cm/s. When the SHP is added to compacted loess, filling and adsorption effects occur: The filling effect decreases the proportion of large pores in the loess. The adsorption effect allows the SHP to encapsulate the loess particles to form a hydrophobic film layer, which leads to the formation of a non-closed hydrophobic structure. This phenomenon decreases the water flow capacity while ensuring the water evaporation capacity inside the loess. The findings demonstrate the potential of adding SHP to enhance the loess impermeability and facilitate and optimize the anti-seepage treatment of various loess filling projects.
... Unfortunately, capillary barriers may need up to four different hydraulically suitable soils; this can increase costs and does not perform well in tropical climates [10]. Nonetheless, it is possible to enhance the capillary barrier by making the coarse layer hydrophobic [5,[10][11][12][13]. ...
... On the other hand, they have been produced artificially by coating particles with a hydrophobic agent. Particles such as natural sands [2,11], synthetic sands [5], or clay [13] have been studied. Effective hydrophobic agents include silanes [42,43], dimethyldichlorosilane [5], polytetrafluorethylene [10], stearic acid [11,44], and oleic acid [2]. ...
Hydrophobic-coated sand causes a reduction in infiltration, making it suitable for hydrophobic capillary barriers. Borosilicate glass waste was crushed into a synthetic sand 180 µm average, and fatty acids (PFA) were extracted from palm oil sludge. The synthetic sand was coated with PFA using mixing (POS-M) and solvent-assisted (POS-S) methods with stearic-acid-coated sand (SA) as a standard at concentrations varying from 1 to 16 g/kg. Contact angle measurements were undertaken by applying the sessile drop method. The water holding capacity of POS-M and SA were determined, and hydraulic conductivity curves were estimated with the van Genuchten model. Finally, a qualitative assessment of POS-M’s effectiveness as a capillary barrier was performed using a set of micro-tensiometers. Maximum contact angles for POS-M, POS-S, and SA were 119.73°, 118.83°, and 107.48°, respectively, and the saturated hydraulic conductivity of hydrophobized sands showed an exponential change of minus 2. Saturated conditions above the capillary barrier and unsaturated underneath were observed. In conclusion, the results indicate that the zero-waste approach applied through the reuse of solid waste from glass and palm oil production can be a waste management alternative in the production of hydrophobic sands that can be used in hydrophobic capillary barrier applications.
... It has been over forty years since the emergence of surface covers and a number of changes have taken place in the materials used for the covers. Among them, the representative ones include Soil Covers [7], Compacted Clay Covers [8,9], and Geosynthetic Clay Liners in covers [10,11]. The main purpose of these kinds of surface covers is to prevent the rainwater from entering into the toxic waste below. ...
Capillary barrier covers consist of fine-grained soil layer overlying coarse-grained soil layer, which are widely used as surface covers for mine tailings, solid waste landfills, and low-level radioactive waste repositories. On one hand, the capillary barrier covers can effectively prevent the rainfall water infiltrating into the toxic and hazardous materials below. On the other hand, the infiltrated water stores and diverts in the fine-grained soil layer, leading to a reduction in the stability of the capillary barrier covers. In this study, a stability analysis method for the capillary barrier covers was established based on the Green-Ampt model and the Janbu method. Firstly, the infiltration process of capillary barrier covers was analyzed and divided into four stages. The variation of the wetting front profile during infiltration, caused by the capillary barrier effect, was depicted based on the law of mass conservation. Next, the wetting front is assumed to be the potential sliding surface. As the infiltration goes on, the stability of capillary barrier covers in different stages was analyzed through the limit equilibrium method. Both the water redistribution and the influence of seepage force in the capillary barrier covers were considered in the proposed method. Finally, using the examples in the published articles, the availability and superiority of the proposed method was verified.
... From the almost unchanging values of the contact angle measurements, it can be implied that the soil particles of the NC-BO and AK-FS soil were sufficiently covered with OS (1:50 for ATS-100 and 1:1000 for Terrasil), while that of IA-PC kept increasing implying insufficient coverage. According to Choi et al. (2016), a constant contact angle does not necessarily imply a maximum amount of grafted OS and the degree of water repellency could further increase with increase in OS concentration. It is important to note that different soils will react differently to OS chemicals, hence it is important to always establish a baseline result from experiments before utilizing any product. ...
The presence of frost susceptible soils makes the design, construction, and maintenance of geostructural systems such as pavement difficult. This pronounced in areas that experience seasonally cold weather characterized by freezing sub-zero temperatures. An innovative approach in mitigation is to render frost susceptible soils hydrophobic. This is achieved by treating soils with cost-effective and environmentally compatible polymers in a process that makes them water repellent (Engineered Water Repellency). This paper investigates the treatment of selected frost susceptible soils using commercially available chemicals (ATS-100, Terrasil, DOWSIL IE6683) at varying concentration dosages. The degree of hydrophobicity imparted, and performance was determined using contact angle measurements and Water Drop Penetration Tests. Treatment using ATS-100 and Terrasil were found to be effective even at small concentrations with values ranging from 73° to 144° for ATS-100 and from 103° to 145° for Terrasil. Effective values for DOWSIL IE6683 were obtained at a ratio of 1:10.
... Work by Keatts et al. (2018) found a trend of increasing apparent contact angle with higher OS dosage rates. Other studies also noted a positive correlation between increasing OS dosages, apparent contact angles and water entry pressures of treated samples (Kim et al. 2011;Keatts et al. 2018;Saulick et al. 2018;Mahedi et al. 2020;Carillo et al. 1999;Wang et al. 2000 andChoi et al. 2016). ...
Organo-silane (OS) modification has been shown experimentally to render soil water repellent. Engineered water repellency has the potential for widespread use in geotechnical and geoenvironmental applications. One such application is mitigating the effects of frost action in susceptible subgrade soils, particularly for unbound, unsurfaced roads. As part of a larger project to evaluate the feasibility of post-construction treatment of such roads, testing was performed with two commercially available OS products at varying dosages. This paper summarizes experimentally observed relationships between treatment, apparent contact angle, and water entry head for four samples of frost-susceptible soil collected from different regions across Iowa. Soil water characteristic curves were used to estimate the prevailing pore size and to relate that to water entry head for a given sample. Modification with two different OS chemicals yielded apparent contact angles between 119° and 143°. The water entry head was determined to range from 15 to 63 cm of water. Inverse relationships were observed between average pore radius and water entry head. These results are expected to be useful to agencies interested in evaluating engineered water repellency for use in new construction as well as rehabilitation of existing infrastructure underlain by frost susceptible soils.
... Hydrophobic polymer-sand composites, herein called hydrophobized sands, have altered hydrological properties such as decreased water infiltration and sorptivity [62,13], suggesting potential in ground interfaces as hydraulic barriers. Choi [10] explored the use of hydrophobic clay as a landfill cover material in evapotranspiration systems. Zheng [62] and Chen [9] extended the use of hydrophobized soils to slope stabilization. ...
Hydrophobized sands have been suggested as materials for hydraulic barriers in infrastructure. When placed at the interface ground–atmosphere, environmental factors such as temperature and rainfall are expected to impact their performance and impair their durability. This study uses accelerated weathering tests to investigate the degradation of industrial sands functionalized with Tung oil, heated Tung oil and dimethyldichlorosilane to render them hydrophobic. Laboratory samples were subjected to thermal ageing, water immersion, cyclic wetting–drying and cyclic freezing–thawing and analysed for their hydrophobic degradation (magnitude and persistency) including controlling mechanisms via surface imaging and analysis. The results revealed that (1) elevated temperature and prolonged water immersion degraded hydrophobicity, albeit with differences between the coatings: dimethyldichlorosilane-treated sands were stable under thermal ageing; (2) a greater concentration of hydrophobizing compounds could minimize hydrophobic degradation during cyclic wetting–drying; (3) freezing–thawing had a negligible effect on hydrophobicity. In order to minimize their degradation, these results suggest that hydrophobized sands can be synthesized by adjusting the hydrophobizing compound and its concentration to suit a specific application.
... Although these structural approaches 26 are effective, they are costly and are prone to problems due to maintenance and environ-27 mental considerations. From a material standpoint, as a practicable alternative, several 28 studies have suggested the possibility of using a hydrophobic (water-repellent) material 29 with water-shielding performance to protect against water infiltration in earth structures 30 [15][16][17][18]. Since methods such as the installation of an impervious layer in engineered 31 slopes using water-repellent geomaterials can be an effective alternative to an instability 32 of slopes due to water infiltration, this study focused on the water-shielding performance 33 4 The purpose of this study is to establish selection criteria for water-repellent sandy 66 soils to improve the water-shielding performance of the impervious layer of engineered 67 slopes. ...
In this study, the selection criteria of water-repellent sandy soils for use in the impervious layer of engineered slopes were examined. First, the hydrophobization of six kinds of sandy soils was performed via the silane treatment. Laboratory experiments to assess hydrophobicity and water-shielding performance—namely the water drop penetration time (WDPT) test, the contact-angle measurement test, and the water infiltration head (WIH) test—were conducted. Based on the required thickness and the required particle number of water-repellent soils, the mean particle sizes of sandy soils that achieved acceptable water-shielding performance were determined. It was found that a Cc value of less than 1.0 or a D40 value of less than 2.0 mm allowed good water-shielding performance in sandy soils. Lastly, some of the measured WIH values agreed with the results estimated by the capillary rise model, and the application of the particle size to this model was discussed.
... Functional materials displaying hydrophobicity have CAs exceeding 90 • e.g. CAs of 124 • , 137 • and 134 • have been reported on hydrophobic sands, silts and clays respectively [1][2][3]. ...
Altering the hydrophobicity of particles allows their use as functional construction materials in ground engineering (e.g. in barriers). This study examines the hydrophobisation of nano to micro particles by using two clays (kaolin and halloysite) and nano silica. To induce hydrophobicity, dimethyldichlorosilane (DMDCS) was used in concentrations varying from 0.25% to 20%. The sessile drop method was used to measure the contact angle (CA) of the particles. Kaolin was initially hydrophobic with a CA of 93 5 ◦ while the other two materials were hydrophilic. The addition of DMDCS to the materials increased CAs of all materials investigated. The maximum CAs recorded at 20% for the halloysite, kaolin and nano silica were respectively: 116 5 ◦ , 143 3 ◦ and 144 6 ◦ . The difference in CAs attained by the clays was attributed to their different structure. Scanning electron microscope-energy dispersive spectroscopy analysis showed increases in carbon content with only halloysite and nano silica after hydrophobisation. The results demonstrate that hydrophobising clays and nano silica can effectively improve their resistance to water infiltration.
