Expansive Clay Research Articles

Influence of Eggshell Ash and Stone Powder on Geotechnical Properties of Expansive Clay in Dukem Town

Expansive clays exhibit a distinctive swelling–shrinkage behavior, leading to structural distress and damage when subjected to varying moisture levels during different seasons. So, to mitigate these issues, stabilization techniques are commonly employed, aiming to diminish swelling tendencies and enhance the strength characteristics of expansive clays. This study delves into the transformative impact of utilizing eggshell ash (ESA) and stone powder (SP) as stabilizing agents on both the index properties and strength parameters of expansive clays. The selection of these stabilizing agents is guided by criteria encompassing cost-effectiveness, availability, and environmental compatibility. Through comprehensive analysis utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD), the mineralogical compositions of both soil and additives are meticulously examined. The XRD analysis of the expansive clay unveils the presence of minerals such as quartz, sanidine (potassium or sodium feldspar), and magnetite. Incorporating ESA into the expansive clay matrix yields substantial improvements across various soil index values, encompassing the free swell index, free swell ratio, linear shrinkage, and unconfined compressive strength value. To further amplify these benefits, the study extends its focus to the influence of SP while maintaining a consistent 6% ESA content. Notably, the addition of SP exhibits a significant enhancement in compressive strength, alongside other crucial properties. Synthesizing these findings, the laboratory results point to an optimal combination ratio of 6% ESA and 15% SP, as a recommended approach to achieve superior stabilization effects. This research contributes to a deeper understanding of the interplay between stabilizing agents and expansive clays, paving the way for improved engineering practices and more resilient structural designs.

Stabilization of Expansive Soil Using Marble Powder and Phosphoric Acid against Physical Properties and SEM-EDS Tests

The Gedebage region faces a myriad of challenges, including road deformations, swelling of roads and bridges, and cracks in drainage foundations, buildings, and asphalt concrete. To address these issues, a comprehensive analysis of soil physical properties was conducted at the POLBAN soil mechanics laboratory, along with chemical tests at the POLMAN laboratory. The primary objective was to understand the physical properties and mineral composition of Gedebage soil and develop effective soil management strategies. Soil stabilization was employed as a method to enhance infrastructure resilience in Gedebage. Marble powder waste (MPW) was utilized in varying concentrations (2.5%, 4%, 5.5%, and 7%) along with 4% phosphoric acid (PA) to optimize the solution. MPW filled soil pores and improved cohesion, while PA reduced moisture content, enhanced particle bonding, increased load-bearing capacity, and minimized soil volume changes. Initial soil tests revealed a high plasticity index (PI) of 54.20%, indicating Gedebage, expansive clay soil nature with significant potential for expansion and plasticity. The AASHTO classified it as "A-7-6", and the USCS classified it as "CH." Stabilization experiments demonstrated that the most effective combination was the original soil + 7% MPW + 4% PA, resulting in a PI of 16.03% and an activity level (Ac) of 0.48. AASHTO classified this combination as "A-2-6," and the USCS as "CL." Furthermore, MPW oxygen, silica, and aluminum content exhibited potential for pozzolanic reactions, while PA reacted with soil mineral cations likes: Ca, Fe, Al dan Phosphor, forming a water-resistant layer. MPW and PA effectively improved the expansive clay soil's ability to withstand moisture-induced changes. This study serves as a foundation for further investigations into the mechanical properties of Gedebage soil, focusing on bearing capacity and stability, using MPW and PA in civil and infrastructure foundation applications.

Vegetation on expansive clay soils from Madrid and La Sagra region (Madrid-Toledo, Spain)

Soils rich in expansive clays (i.e., smectite and montmorillonite, and, to a lesser extent, soft clays such as sepiolite and palygorskite) are found in a broad stretch running NNE-SSW from the east of Madrid to the Tagus River surrounds in the province of Toledo. These clays tend to give rise to a specific type of soil, known as "vertisols" or related argillic soils with vertic behaviour, varied chemical and sedimentological composition, and occasionally siliceous or dolomitic clasts. In these soils, where there is an absence of woody vegetation, the colonising nitrophilous vegetation becomes of particular interest through the usage and alteration of the land. These argillic soil plant communities are incredibly diversified, with flora suited to the unique hydrogeochemical conditions of these settings. The variety of these plant communities is determined by factors such as land use, lithology, terrain, and the level of humidity they can withstand. We identify the primary plant community on the Madrid-Toledo expansive clays in this paper, as well as provide a preliminary approach to the different varieties and transitions to other related plant communities. The main dynamic and catena links are established, and a floristically summarised table is provided, along with a descriptive examination of the community's behaviour and variability. Finally, its conservation status and the high degree of threat to which it is subjected are assessed.

Resilient response and strength of highly expansive clay subgrade stabilized with recycled concrete aggregate and granulated blast furnace slag

In urban areas, due to urban development and lack of space, roads may be built on the expansive clay subgrade. Expansive clay soils increase in volume when in contact with water and shrink by losing water. Recycled concrete aggregates (RCA) are one of the components of construction and demolition (C&D) wastes that can be used instead of natural resources in road construction projects. In this research, a combined method of mechanical and chemical stabilization was used to evaluate the use of RCA as a mechanical stabilizer and granulated blast furnace slag (GBS) as a chemical stabilizer to improve the strength and resilience characteristics of expansive clay subgrade. Laboratory results showed that adding RCA wastes to expansive clay subgrade reduced atterberg limits (LL, PL, and PI) and optimum water content (OWC) and increased the maximum dry density (MDD), California bearing ratio (CBR), and uniaxial compression strength (UCS). Expansive clay subgrade with 20 % RCA was treated with GBS chemical stabilizer in order to achieve a minimum 7 days target strength of 1.7 MPa for subbase application. A series of repeated load triaxial (RLT) tests were performed according to the AASHTO T307 procedure and resilient modulus (Mr) values of the stabilized clay subgrade specimen were evaluated at different curing times under cyclic loading. Also, the proposed Mechanistic-Empirical pavement design Guide (MEPDG) model was used to predict Mr values in different confining and deviator stresses which showed a good correlation with the measured Mr values. Finally, the improvement of the clay subgrade stabilized with RCA and GBS was also supported by SEM analysis. The results obtained from this research showed that the use of RCA, in addition to reducing disposed waste and environmental pollution, can improve the physical and mechanical characteristics of expansive clay Subgrade layers.

Engineering properties and mechanical behaviour of problematic soil stabilized by bituminous oil shale ash

This paper investigates the viability of stabilizing expansive brown clays in the Northern region of Jordan using a local bituminous oil shale ash from El-Lajjun, Jordan. A comprehensive experimental programme was designed to i. examine the impact of oil shale ash dose by weight on the strength gain. ii. Evaluate oil shale ash stabilized clays' consolidation and volume change behaviour during loading and unloading. Results revealed that adding 20 % bituminous OSA remarkably improved expansive brown clays' engineering properties and mechanical behaviour. An increase of 140 % in the unconfined compressive strength and a reduction of 19.3 % in the permeability coefficient was obtained at 20 % OSA. Also, the Unconfined Compressive Strength tests revealed that the strength of OSA-treated expansive clays is significantly affected by the curing time. Increases of 35.1 % and 65.7 % in the unconfined compressive strength were achieved after 7 days and 21 days of curing, respectively. Furthermore, the addition of OSA showed an effect on compressibility behaviour, reducing settlement. Regarding the consolidation parameters, the inclusion of 20 % OSA reduced the compression index (Cc) and swelling index (Cs) by 42.67 % and 72.6 %, respectively.

Study on Mechanical Properties of Deep Expansive Soil and Coupling Damage Model of Freeze–Thaw Action and Loading

This study is primarily intended to present a damage constitutive equation under the combined action of confining pressures and freeze–thaw cycles by subjecting deep expansive clay to the consolidated undrained triaxial tests. We study the influence of the numbers of freeze–thaw cycles on various mechanical indexes of soil by using the TSZ-2 instrument (fully automatic triaxial instrument). As the number of freeze–thaw cycles increases, the ultimate peak stress of the soil decreases, and then, the effect of the freeze–thaw effect on the shear strength gradually weakened. By combining the expression method of the damage variable under the action of loading alone with the expression method under the action of freeze–thaw cycles alone, we brought in the damage evolution equation to obtain the damage constitutive equation under the combined action of confining pressures and freeze–thaw cycles. The stress values under three confining pressures (100 kPa, 200 kPa, and 300 kPa) can be determined by using the final damage constitutive model. The measured data with a water content of 17% and six freeze–thaw cycles were compared with the theoretical data. The actual strength values were 118.4 kPa, 152.3 kPa, and 184.1 kPa, and the theoretical strength values were 120 kPa, 150 kPa, and 186 kPa. The fitting degree of the strength value was as high as 99%, which verifies the feasibility of this model. This study can serve as an available reference for well wall construction and disaster prediction in deep coal mining.

Swelling Behavior of a Clay-Pellets Mixture Intended for the Isolation of Spent Nuclear Fuel

Deep geological repository is the most favorable option for the safe disposal of high-level nuclear waste (HLW) and spent nuclear fuel (SNF). The design of such a facility relies on the multi-barrier system, encompassing a cylindrical metallic container (encapsulating the HLW/SNF), an engineered barrier system (EBS, around the metallic container); and the host-rock (or natural barrier). The most preferred buffer material to construct the EBS is bentonite clays. They are being considered as potential buffer materials because of, amongst other reasons, their high swelling capacity provides mechanical stability to the metallic canister containing the HLW/SNF; their good thermal conductivity assists to dissipate the heat released by the HLW/SNF; their low permeability delays the flow of water and gas through the system [1].
 Bentonites are highly swelling smectites clays that exhibit significant volume increase when wetted under free-swelling conditions, and develop high swelling pressure upon soaking when the volume change is restricted. It is envisaged that the EBS will be built using blocks of compacted bentonites (Figure 1(a)), or a combination of high-density clay-pellets mixtures and blocks of compacted bentonites (i.e., where the metallic container sits, Figure 1(b)). Clay-pellets are also considered as possible seal materials to fill gaps that will be present in this type of system, e.g., the gap between the EBS and the surrounding host-rock [2]. Therefore, a better understanding of the swelling capacity and behavior of the bentonite in these two forms (i.e., compacted-clay and clay-pellets mixtures) is critical for a proper design and evaluation of the long-term performance of geological repositories for HLW/SNF.
 Most of the research conducted in this area has been mainly focused on compacted bentonites looking, e.g., at the influence of several factors on their swelling pressure capacity, namely, type of clay minerals, initial dry density, water content (or degree of liquid saturation), and type of water [3]. More recently, investigations have been conducted to study the behavior of high-density pelletized clay mixtures [4, 5], however, relatively less attention has been placed in this type of material. Clay-pellets presents a number of advantage, e.g., they are very suitable for filling (small) technological voids (Figure 1(a)), there is no need for additional in-situ compaction when they are used as a buffer/backfill material (Figure 1(b)), and it is relatively easy to manufacture them.
 The granular clay-pellets samples were manufactured, and the constant volume cells were developed at Texas A&M University to investigate the swelling behavior of expansive clays. It has been shown in figure 2 that both materials (compacted clay and pelletized clay) developed similar maximum values of swelling pressures. However, the patterns associated with the swelling pressures evolutions are different, owing to the different pore structures associated with these two materials, which impact on the kinetic of clay hydration and swelling pressure evolutions. The aim of this research is to gain a better understanding of the swelling pressure behavior of clayed materials intended as potential barriers materials for the safe isolation of the HLW/SNF.

Mechanical Properties of Expansive Soil Stabilized by Sand

Expansive clay soils have swelling and shrinkage properties and somehow reduce the mechanical properties required for soils to be used in civil engineering works. One method to improve the soil is by mechanical stabilization, namely mixing expansive clay soil with sand material. The sand material used in this research varied by 7.5%, 15%, and 22.5% of the total dry weight of expansive clay. The results shows that changes in mechanical properties were observed from the compaction test and California Bearing Ratio (CBR) both for soaked or unsoaked test. Based on these variations, in the compaction test, the addition of sand variations increases the maximum dry unit weight value and generally reduces the optimum water content value. The same results were also seen in the soaked and unsoaked CBR tests. In the swelling potential test, the addition of sand material succeeded in reducing the swelling value in expansive clay soils.

Modification of Expansive Clay Behavior by Using of the Filtration Effluent of the Water Treatment Plant

Modification of Expansive Clay Behavior by Using of the Filtration Effluent of the Water Treatment Plant

Fast-nondestructive measurement of axial slice water content and water distribution with NMR SFG-MSCPMG sequence

Measuring hydraulic conductivity by instantaneous profile method needs to detect the pore water content of soil at different positions, but most of the detecting methods will disturb the soil sample. In the study, the axial slice scanning of soil samples was carried out by using static filed gradient multi-slice Carr-Purcell-Meiboom-Gill (SFG-MSCPMG) sequence of nuclear magnetic resonance (NMR) technology, which can nondestructively determine water content and distribution at different positions of soil column. In this experiment, three clays were used to illustrate the relationship between NMR test results and oven drying results of water content. The results show that there is a good linear relationship between the NMR signal and water content. Combining mercury intrusion porosimetry (MIP) data, the transverse surface relaxivity parameters (ρ2) of clays are obtained. With ρ2 = 41.90 μm/s the T2 distribution curve of pore water in the ordinary clay can be converted into the pore water distribution curve, which is in good agreement with that obtained with MIP. Nevertheless, it is found that the T2 distribution curve of pore water in expansive clay obtained with NMR technique is more suitable for analyzing the average pore water distribution because of the fast exchange of pore water between the interlayers, intra-aggregates and inter-aggregates in expansive clay.

Stress relaxation behavior of an expansive clay under low confining pressure: experimental characterization and predictive modeling

Stress relaxation behavior of an expansive clay under low confining pressure: experimental characterization and predictive modeling

Effects of initial compaction condition and temperature on swelling characteristics of compacted bentonite

Given that isolated high-level radioactive waste repository cannot be modified during operation, understanding the influence of the buffer's initial conditions is critical. This study investigates the influence of the initial dry density and water content on the swelling pressure and consolidation characteristics of Korean bentonite, which is a buffer candidate in the engineered barriers of the repository. In order to consider the high temperature repository condition, samples of various dry densities and water contents were tested at different temperature. Prediction models were developed using the test data and the models were used to analyze the effects of initial conditions. The research findings indicate that the influence of dry density, water content, and temperature on swelling pressure is not absolute and can show different tendencies depending on the case. In terms of consolidation behavior, the compression index and pre-consolidation pressure differ with dry density and temperature, while recompression is unaffected. The study's results align with prior research on compacted expansive clays, with the double structure of clay serving as a suitable explanation for the swelling phenomenon's dependence on the initial compaction condition.

Geopolymer-stabilized soils: influencing factors, strength development mechanism and sustainability

This paper presents the strength and micro-structural characteristics of high plasticity expansive clay stabilized with ordinary Portland cement (OPC) and geopolymers. Furthermore, sustainability aspects such as cost-efficiency, energy consumption and eco-efficiency of the OPC and geopolymer-stabilized soils were compared. The experimental results revealed that the geopolymer-stabilized soils exhibit higher strength and sustainability performance than the OPC-stabilized soils. This study also explores the developed machine learning prediction models of the geopolymer soils’ unconfined compressive strength (UCS) based on experimental data from current research and previous literature. Linear regression (LR), K-nearest neighbour (KNN), random forest (RF), random forest with random search hyperparameter optimization (BRRF) and random forest with grid search hyperparameter optimization (BGRF) were used as part of ensemble algorithms to predict stabilized soils UCS. Eight parameters such as liquid limit (LL), plasticity index (PI), ground granulated blast furnace slag (S) content, fly ash (FA) content, the molarity of NaOH (M), activator to binder ratio (A/B), Na/Al and Si/Al were used as input to predict UCS of geopolymer soils. The following metrics were used to assess the models’ predictive ability for compressive strength: coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE) and mean square error (MSE). The BRRF model has a good potential to predict the UCS of geopolymer soils, according to the findings of its testing (MAE = 0.27, MSE = 0.21, RMSE = 0.46, R2 = 0.99) and training (MAE = 0.78, MSE = 1.48, RMSE = 1.23, R2 = 0.96) phases. According to the RF model's feature importance study, slag content and liquid limit were found to influence forecasting compressive strength, while fly ash content has the least influence.

Experimental investigation on the effect of initial structure on the water retention behavior of Mile clay

Soil structure has strong effect on hydro-mechanical properties of soils, particularly in the case of expansive clays. Along the wetting–drying path, expansive clays undergo significant volume changes that can pose serious challenges for infrastructures built on them. Moreover, the hydro-mechanical behaviour of intact, compacted, and reconstituted expansive clay exhibits notable differences. In this study, the effect of natural soil structure of intact Mile expansive clay on water retention behaviour was studied by comparing two states of Mile clay, intact and compacted states. The corresponding water retention behavior along the main wetting and drying paths were analysed and compared. Utilizing scanning electron microscope and mercury intrusion porosimetry tests, the different water retention behaviours observed between intact and compacted Mile clay were further elucidated from a microstructural aspect. It shows that bonding between and within soil aggregates in intact Mile clay constrained volume changes in specimens along the drying and wetting paths. Along these paths, the volume of micropores in intact specimens was consistently larger than that of compacted specimens, resulting in a good water retention behavior, particularly along the main wetting path. Volume changes of intact and compacted specimens were primarily driven by changes in macropore volume. Only when specimens become unsaturated, the changes in micropore volume became significant. At very high suction, the effect of bonding between and within soil aggregates diminished, which was possibly due to the destruction of bonding, resulting in similar water retention properties for intact and compacted specimens.

Stabilisasi Tanah Ekspansif Menggunakan Limestones Sebagai Subgrade Perkerasan Jalan Pada Proyek Jalan Tol Seksi 6a Paket Sumedang – Dawuan

The problems that occur in the Toll Road Project Section 6a of the Sumedang – Dawuan package are subgrade soils including expansive soil types. Where the type of expansive soil is a soil type that is not good with very high clay content, expansion and shrinkage. This potential for shrinkage causes less stability in the road construction so that it affects the safety and comfort of traffic. The general technical properties of expansive soils are that they have a fairly high moisture content and low bearing capacity. Because of these properties, expansive soils are classified as poor soils to be used as subgrades. One way to overcome this is by improving the soil or so-called soil stabilization. In this study, the material used for stabilizing the expansive soil is limestone. Limestone or limestone is a carbonate rock that is formed biologically and biochemically.This research was conducted with the aim of knowing the effect of adding limestone to the physical properties of expansive clay and knowing the optimum level of addition of limestone so as to produce a maximum increase in the stability of the road construction subgrade. The research method used is the experimental method. The study was designed with 5 treatments, namely 0%, 25%, 50%, 75% and 100% of the use of limestone on expansive clay soil.The results showed that the use of limestone as a stabilizing agent for clay in the Section 6a of the Sumedang – Dawuan Toll Road Project affects the physical and mechanical properties of the expansive clay. Where the higher the addition of limestone, the smaller the liquid limit (LL), plasticity limit (PL), moisture content and swelling, while for specific gravity, compaction and CBR the higher. The use of limestone in the Toll Road Project Section 6a Sumedang – Dawuan Package optimum 75% with a ratio of 25% expansive clay with a CBR value of 3.75% < 6% (Minimum requirement of CBR value for road pavement subgrade) and produces a development value ( swelling) 3.85% > 1.25% (maximum limit conditions for pavement subgrade swelling). The CBR value and swelling (swelling) do not meet the requirements as a subgrade for road pavement, in accordance with the expressway technical specifications for a minimum subgrade density of 100℅, a minimum CBR of 6℅ and a maximum swelling of 1.25℅.

Enhancement mechanism of remolding on the swelling behavior of expansive stiff clay: from microstructure perspective

Enhancement mechanism of remolding on the swelling behavior of expansive stiff clay: from microstructure perspective

Response of High Swelling Montmorillonite Clays with Aqueous Polymer

Expansive clays containing mineral montmorillonite exhibit swelling and shrinkage due to variations in the moisture content, leading to significant distresses. There has been a growing interest in chemical and polymer additives treated for high swelling montmorillonite clays in recent years. However, limited attention has been paid to the effect of polyacrylamide on the soil’s swelling behavior. Moreover, nontraditional methods of the soil treatment are applied for the rapid stabilization of soil. In this article, polyacrylamide polymer is used as an additive to expansive clays to control the swelling phenomenon. Three different percentages—2.5%, 5%, and 7.5%—of polymer are blended with oven-dried soil to determine Atterberg limits, compaction features, and swelling characteristics. Additionally, electrical impedance measurement is conducted on treated soil samples with different moisture contents. The electrical resistance of soils and polymer-treated soils is measured based on the electrical resistivity correlation of soils. Tests results for soils stabilized with polyacrylamide show that swelling is significantly reduced with increasing the additive content. Moreover, the addition of polymer improves resistivity of soil. Aqueous polyacrylamide can be utilized as an effective stabilization additive to enhance properties of expansive clays.

Performance of clay soil reinforced with PET plastic waste subjected to freeze-thaw cycles for pavement subgrade application

The freeze-thaw (F-T) cycle is a common weathering process that often occurs in cold climates, and it can deteriorate the mechanical performance of the subgrade soil, leading to pavement failure and economic loss. Plastic wastes have been adopted as a soil reinforcement element to improve the geotechnical properties and stability of expansive clay soils used as subgrade material. Previous research has mainly focused on the application of polyethylene terephthalate (PET) plastic waste to soil reinforcement under ambient temperature, but few studies have investigated the geotechnical performance of expansive clay soils reinforced with PET plastic waste under freeze-thaw conditions for pavement subgrade application. Moreover, there is a lack of knowledge on the dynamic properties of expansive clays modified with PET plastics exposed to the F-T process. This study conducted a series of mechanical experiments, including repeated load triaxial tests and unconfined compressive strength tests, for the first time to investigate the mechanical performance of expansive clay soil reinforced with different percentages of PET strips (i.e., 0, 1, 1.5, and 2% by the weight of dry soil) after being exposed to 0, 2, 5, and 8 F-T cycles. The experimental results showed that the F-T process significantly reduced the compressive strength and resilient modulus. However, the compressive strength and resilient modulus of the PET strips-reinforced samples were higher than those of the unreinforced samples after F-T cycles. The optimum content of PET strips was found to be 1% by weight of dry soil, as it exhibited the highest strength and stiffness under various F-T cycles.

Potential of tropical expansive clays as natural sealing layer in nuclear waste repository system: a preliminary study

The issue of radioactive waste disposal in Malaysia is frequently debated, particularly in terms of human and environmental long-term well-being. The creation of a repository with minimal hazard risk and cost implications is a major environmental concern related to nuclear waste. Expansive clay has distinct characteristics that are readily available in the environment and can serve as a natural barrier (sealing system) against the migration of radioactive and chemical pollutants. In this study, the physico-chemical and microstructural properties of 2 types of tropical soils with dominant clays mineral (vermiculite and montmorillonite) were investigated to better understand the potential of these clays as natural sealing in nuclear waste repository systems. Based on preliminary findings, both types of soil have been classified as alkaline soil (>7) with high swelling capacity (FSI) (>80%) and high consistency (LL>50%; PI>30%). The microstructural study demonstrates that vermiculite clays have a noticeable flaky morphology and a porous structure as compared to montmorillonite, indicating that the soil can absorb more water, hence decreasing its infiltration capability. Pinhole dispersion analysis reveals that montmorillonite clay is more prone to dispersion due to the presence of sodium ions and has a higher erosion potential than vermiculite clay. Future Malaysian stakeholders may employ this research to establish a long-term plan for the management of radioactive waste through the usage of natural resources.

The Role of Stress States on the Hysteric Behavior of Expansive Soil under Multiple Drying-Wetting Cycles

Expansive soils in the field are typically exposed to cyclic wetting and drying due to climatic fluctuations and subjected to a variety of stress conditions in nature or when used as compacted layers for the construction of hydraulic barriers or waste disposal facilities. The hysteric behavior of the soil-water characteristic curve (SWCC) is a key parameter for understanding, modeling, and interpreting the unsaturated behavior of these soils under such conditions. This study investigates the effect of stress states on the hysteresis behavior of soil-water characteristic curves (SWCCs) for compacted highly expansive clay over a range of matric suction between 0 and 1500 kPa. Two test series were performed, the first test series investigated the effect of stress states on the hysteresis of SWCCs during a single drying-wetting (DW) cycle. The second test series studied the combined effect of stress applied and multiple drying-wetting cycles on the SWCC hysteresis. For the sake of comparison, the overall SWCC hysteresis due to drying-wetting cycles was quantified using the average degree of hysteresis in terms of volumetric water content (ADHθ). Furthermore, contributors to the observed hysteresis were defined using two newly proposed measures; namely, average degree hysteresis in terms of gravimetric water content (ADHw) and in terms of volume change (ADHe*). The outcomes of this study indicate that consideration of stress states on the hysteresis of SWCC for expansive clay is of great importance. The results show a dual trend for the variation of ADHθ with applied vertical stress. Furthermore, multiple DW cycles induced a significant reduction in the hysteresis (ADHθ) under low- and high-stress states up to a certain level of DW cycles, then, no further changes in the hysteresis trend were detected. It was also found that hysteresis loops under a low-stress state were concentric in shape while hysteresis loops for specimens under a high-stress state were non-concentric, with a downward shift in hysteresis loops with the increase in DW cycles.