Biopolymer-treated Soil Research Articles

Compacted Soil Liners and Covers for Waste Containment

An effective waste disposal system is essential in preventing the infiltration of leachate into the ground and achieving the sustainable development goal of ensuring access to clean and potable water. Liner is an important component of landfill in waste disposal facilities as it impedes the flow of leachate from the landfill. The choice of liner material depends on factors, such as the type and availability of soil, the site conditions, sustainability, and cost-effectiveness. This paper focuses on different soil types as compacted liners in waste containment facilities. The main purpose of this paper is to present the findings of laboratory investigations and measurements of hydraulic conductivity and other important soil properties extracted from previous literature with the aim of providing a guide in material selection for use as compacted soil liners and covers in waste containment applications. The key results of many laboratory studies previously conducted on soils of different properties, gradation, plasticity, and mineralogy, untreated or stabilized with various additives such as waste materials from industries, agricultural by-products and municipal waste materials are reported. The paper also presents the potential of using biopolymer-treated soils (soils modified by polymers) derived from plants and animals, as potential liner materials.

Target reliability-based design optimization studies on cohesive soil amended with chitosan and casein for liner applications

The current study investigated the primary and secondary compressibility characteristics of organic clay with two biopolymers, Chitosan (Dch) and Casein (Dca) at dosages of 0.5%, 1%, 2%, and 4%. The primary compression index (Cc) values were reduced by 18% and 59% at dosage (Dch and Dca) of 4% at a consolidation pressure of 800 kPa. The secondary compression indices of chitosan and casein-treated soils fell below the normal range specified for organic soils and lay in the range of 0.01–0.017. The biopolymers also accelerated the consolidation process at all dosages (Dch) and 2% Dca. The hydraulic conductivity increased for all dosages of chitosan whereas it declined for all dosages of casein compared to untreated soil. The reliability analysis was conducted for biopolymer-treated soils and presented a rational approach toward the selection of a suitable liner. Chitosan failed to achieve a target reliability index of 3 whereas casein-amended samples attained values equal to and greater than 3 at all dosages and consolidation pressures at COV of Kmax = 20%. At all dosages, the casein-treated soils exhibited reliability index values greater than 3 up to COV of Kmax = 40% indicating the higher stability of casein mixes as a liner material.

Investigating combined effects of saturation–desaturation cycles and cyclic stress resistance of reinforced biopolymer-treated soil

Throughout their service life, subgrades endure significant stress from cyclic traffic and seasonal moisture fluctuations. This study aims to evaluate the moisture variation and cyclic stress resistance of reinforced and biopolymer-treated soils, which were treated with varying percentages (0.25%, 0.5%, 0.75%, and 1.0%) of xanthan gum (XG) and sisal fiber, to determine the level of tolerance a subgrade can sustain. Wetting–drying (W-D) cycle tests, unconfined compressive strength (UCS) tests, and dynamic resilient modulus (DRM) tests were conducted to assess the resistance of the treated soils to moisture variation and cyclic stress. The findings indicate that biopolymer-treated specimens retained over 95% of their original mass after 15 cycles, whereas fiber-reinforced soil exhibited a 9.1% loss in mass. Furthermore, the DRM of the reinforced soil improved, demonstrating greater resistance to cyclic stress compared to biopolymer-treated soils. Fiber-reinforced soils exhibited strain-hardening responses at low cyclic stress levels and maintained stress tolerance even at high cyclic stress levels without signs of strain deformation. Conversely, the UCS of the biopolymer-treated soil surpassed that of the fiber-reinforced soil due to the brittleness of the specimens.

Investigation of Bridge Scour Mitigation with Nature Binding Materials: Biopolymers

The use of biopolymers to tackle geotechnical problems is an essential step toward the development of sustainable geotechnical systems. The strength and erosion resistance of biopolymer-treated Hot Coffee soil sampled from the bridge site in Jackson, Mississippi were examined in this research. The optimum biopolymer concentration and moisture content were tested for Agar Gum, Xanthan Gum, and Guar Gum treatment of Hot Coffee soil, respectively. The mechanical behavior and erosion resistance of biopolymer-treated soil samples were evaluated through the unconfined compressive strength test, splitting tensile test, triaxial test, and pocket erodometer test. The results indicated that all three biopolymers improved Hot Coffee soil strength, but Guar Gum improved soil unconfined compressive and tensile strength greatly. The addition of 1% Guar Gum can improve the unconfined compression stress (UCS) and split the tensile strength of Hot Coffee soil to roughly 4,000 kPa and 600 kPa, respectively. At the same time, the cohesion of Hot Coffee soil treated with biopolymer was enhanced. The cohesion of the soil treated with 1.5% Xanthan Gum increased from 0 to 41.5 kPa. In addition, the erosion resistance of biopolymer-treated soil was also increased. With a 1.5% Xanthan Gum addition, the erosion resistance level of Hot Coffee soil reduced from very high erodibility to medium erodibility. Therefore, biopolymers have great potential for bridge scour mitigation.

A Novel Prediction of Strength Properties of Biopolymer-Treated Soil: A Response Surface Approach

A Novel Prediction of Strength Properties of Biopolymer-Treated Soil: A Response Surface Approach

Sustainable soil treatment: Investigating the efficacy of carrageenan biopolymer on the geotechnical properties of soil

The employment of novel biopolymers offers geotechnical engineers a diverse range of materials to choose from, depending on the specific requirements of different projects. Regarding the promotion of environmentally friendly materials in the construction industry, this study introduces carrageenan as a novel biopolymer for soil improvement. The research also includes a comparative study of carrageenan's performance with xanthan which is the most commonly used biopolymer in geotechnical engineering. Unconfined compressive tests (UCS) were conducted to evaluate the performance of biopolymer-treated soil samples over a variety of effective parameters including biopolymer content, moisture content, curing time, soil particle size, and durability under wet-dry cycles. In order to explore the soil size effect, kaolinite silt and sand were combined in various proportions and treated with different biopolymer ratios to enhance strength development. The optimal mix of each biopolymer-treated soil was then exposed to five cycles of wetting and drying. Carrageenan improved the compressive strength of untreated soils in all cases, for example 3.4 times for 0.5% (wb/ws) of biopolymer. In higher proportions of kaolinite, carrageenan performed considerably better than xanthan gum in terms of compressive and shear strength. In addition, with an emphasis on confining pressures, static triaxial experiments were conducted to examine the effectiveness of carrageenan, by which it was shown that carrageenan outperforms xanthan in terms of shear strength especially in the fine-grained soil. The mechanism and chemical interaction behind the significant performance of carrageenan in binding soil grains, increasing mechanical strength and improving durability of the soil was also studied through FTIR analysis and scanning electron microscopy (SEM) images. It can be concluded that carrageenan can be considered as a sustainable alternative to conventional materials such as cement and lime.

A Review on Soils Treated with Biopolymers Based on Unsaturated Soil Theory.

Adding different materials to soil can improve its engineering properties, but traditional materials such as cement, lime, fly ash, etc., have caused pollution to the environment. Recently, biopolymers have shown many advantages, such as economy and environmental protection, which make them applicable to geotechnical engineering. This study summarizes the effects of biopolymers on soil's engineering properties and the main directions of current research. Firstly, the advantages and disadvantages of a variety of widely used biopolymer materials and their effects on the specific engineering characteristics of soil (i.e., water retention characteristics, strength characteristics, permeability characteristics, microstructure) are introduced, as well as the source, viscosity, pH, and cost of these biopolymers. Then, based on the theory of unsaturated soil, the current research progress on the water retention characteristics of improved soil is summarized. The key factors affecting the strength of biopolymer-treated soil are introduced. Due to the actual environmental conditions, such as rainfall, the permeability and durability of biopolymer-treated soil are also worthy of attention. In summary, it is necessary to study the variation laws of the engineering properties of biopolymer-treated soil in the full suction range, and to predict such laws reasonably. The relevant results are conducive to the safer and more scientific application of biopolymers in geotechnical engineering practice.

Water-retention behaviour and microscopic analysis of two biopolymer-improved sandy soils

Soil erosion in the Yellow River basin in China has seriously affected the stability of the foundations of civil engineering structures. Traditional treated materials used for preventing the soil erosion are often harmful to the environment. Biopolymers have been widely used for soil improvement because of their low cost, environmental friendliness, and feasible application. However, most studies on the water-retention behaviour of treated soils conducted to date have focused on the low or high suction range, while few have examined the behaviour over a wide suction range. Converting the saturated state of treated soils into unsaturated state until it is completely dry will lead to changes in the water retention behaviour of biopolymer-treated soils. Therefore, this study investigated variations in the water-retention behaviour and micromechanism of biopolymer-treated sandy soils over a wide range of suction. Specifically, the water-retention behaviour of treated soil was tested using a pressure plate apparatus in the low suction range and a WP4C apparatus in the high suction range. Scanning electron microscopy was also used to evaluate water-retention mechanism of soils treated with different ratios of biopolymer. Biopolymers were found to absorb water to form hydrogels and biofilms, which reduced the pore spaces between soil particles and improved the water storage ability of sandy soils. The water-retention capacity of both Xanthan gum and Gellan gum-treated sandy soils was higher than that of untreated sandy soils, and increased as the biopolymer ratio increased. The water-retention behaviour of the Gellan gum-treated sandy soil were better than that of the Xanthan gum-treated sandy soil. Finally, a prediction model of the soil–water retention curve that considered the biopolymer ratio was proposed based on the Fredlund-Xing model. This study provides a scientific basis for the application of biopolymers to control soil erosion in the Yellow River basin in China.

Xanthan gum biopolymer-based soil treatment as a construction material to mitigate internal erosion of earthen embankment: A field-scale

Biopolymers, which are naturally produced polymers, exhibit hydraulic and mechanical properties, and have low environmental impact. Therefore, they can be employed as an alternative to conventional civil engineering materials for internal erosion prevention. However, the internal erosion behavior of biopolymer-treated soils in a full-scale embankment is yet to be thoroughly investigated. This study focused on the potential of using xanthan gum biopolymer for internal erosion control in earthen embankments. To this end, both laboratory and full-scale investigations were conducted for analyzing its influence on the prevention of internal erosion. The laboratory tests showed that a 1% xanthan gum treatment demonstrated optimal characteristics for embankment building with enhanced soils’ plasticity and mechanical strength. Full-scale embankments were constructed using both untreated and 1% xanthan gum treated earthen materials with simulated internal erosion beneath the box culvert to test the effect of xanthan gum on mitigating internal erosion. The results revealed that xanthan gum successfully minimized the expansion of internal erosion through particle bonding, enhanced apparent cohesion, and pore-clogging. The untreated embankment eroded rapidly via seepage flow and collapsed within 1,500 s, while the 1%-XG-treated embankment retained its structure without considerable erosion until 2,500 s. Thus, xanthan gum is an environmentally friendly construction material that can achieve sufficient embankment stability with a small weight ratio (1% of total soil).

Rheological behavior of zein biopolymer and stiffness characteristic of biopolymer treated soil

The modification of polymeric biomolecules to achieve improved cementation is important for their potential applications. This study presents the rheological behaviors of eco-friendly zein biopolymer and stiffness characteristics of biopolymer-treated soil under various solvent and curing conditions. The rheological and stiffness characteristics of zein biopolymer are evaluated in terms of shear stress, viscosity, and shear wave velocity. The time sensitivity, flow index, and microstructure of biopolymer gel are analyzed. The biopolymer gel generally exhibits a weakly non-Newtonian shear-thickening behavior, except for the specimen cured for 24 h under chamber condition. At a constant shear rate, the biopolymer gel shows a rheopexy behavior, which is characterized by an increase in viscosity over time. The shear wave velocity of biopolymer-treated soil increases with the curing period, up to 50 and 96 % under atmospheric and chamber conditions, respectively. The peak absorption values for the hydroxyl functional group decrease significantly as the curing period and ethanol content increase. Furthermore, the microparticle sizes of the zein biopolymer gel decrease with increasing ethanol content. Therefore, understanding the stiffness characteristics of biopolymer-treated soil specimens for potential soil stabilization can be improved based on the rheological properties of zein biopolymer.

Water-retention properties of xanthan-gum-biopolymer-treated soils

This study aimed to estimate the effects of the xanthan gum biopolymer on the wetting and drying processes of soils. Xanthan gum with different contents by the mass of dried soil was used to treat Jumunjin sand and sand-clay mixtures. The wetting and drying soil-water characteristics of xanthan-gum-biopolymer-treated sand were investigated using capillary rise open tubes and a Fredlund-type soil-water characteristic curve device, respectively. The results show that xanthan gum has a significant effect on controlling the movement of water in soil. The xanthan gum biopolymer shapes the drying soil-water characteristics of soil, and there is a non-linear relationship between the xanthan gum content and the soil-water characteristic parameters of the treated soils. Xanthan gum significantly reduces the capillary conductivity of soil down to 10−7–10−8 m/s for soil treated with 1.0% xanthan gum. Xanthan gum affects the capillary equilibrium process of water differently in wetting tests as well. Furthermore, the wetting results show the role of clay particles in the flow-controlling performance of xanthan gum.

The Effects of Particle Size Distribution and Moisture Variation on Mechanical Strength of Biopolymer-Treated Soil

Biopolymers have recently shown great potential to replace traditional binding materials in geotechnical engineering; however, more research is required to reach a deeper understanding of biopolymer-treated soil behavior. The objective of this study was to investigate the most important parameters that affect the behavior of biopolymer-treated soil, including biopolymer content, dehydration time, soil type effect, and durability. Sodium alginate and agar biopolymers were used due to their stability under severe conditions and the reasonable costs to study these parameters. A broad range of soil particle sizes was used to optimize the kaolinite-sand combination. As one of the main concerns in the behavior of biotreated soils, durability was investigated under five cycles of wetting and drying. In addition, a comprehensive microstructural study was performed by FTIR analysis and SEM images, as well as chemical interaction analysis. The results indicated that the optimized biopolymer content was in the range of 0.5-1% (to soil weight) and the dehydration time was 14 days. A soil combination of 25% kaolinite and 75% sand provided the highest compressive strength. Under wetting and drying conditions, biopolymers significantly increased soil resistance against strength reduction and soil mass loss. This study provides an understanding how agar and sodium alginate changes the behavior of the soil and can be used as a reference for further studies in the future.

Performance Evaluation of Polysachharide based Biomaterials for Sand Stabilization

Recent research on soil improvement have showed that the use of biopolymers can significantly enhance the various engineering properties of the soil. Soil improvement using biopolymers has attracted considerable attention in recent years, with the aim to reduce the harmful environmental effects of traditional materials. This report aims to provide a review on the environmental assessment of biopolymers as binders in soil improvement, biopolymer-treated with soil characteristics, as well as the most important factors affecting the behavior of the treated soil. Various geotechnical properties are evaluated and compared, including the unconfined compressive strength, and durability of biopolymer-treated soils. The usage of biopolymers has positive effects on the soil in the form of enhanced strength, However, a thorough understanding of the geotechnical qualities is required in order to completely apply the biopolymer technology to the fields. Biopolymer kinds, soil types, biopolymer contents, curing times, thermal treatment, and mixing techniques all play a significant role in how effective biopolymers are at improving the ground. In this part of study, the pycnometer method, sieve analysis, standard proctor compaction tests, unconfined compression test, durability, gel plug tests, pH test, and FTIR test, were used to understand and analyze the pectin-treated sand. Keywords: Pectin,Geotechnical Engineering,Bio Polymer- Treated soil

Effects of Xanthan Gum Biopolymer on Soil Mechanical Properties

The necessary application of sustainable engineering methodologies has been increasing as the number of environmental hazards caused by global warming is on the rise. Cement as a traditional common additive for soil improvement has several negative impacts on the environment. This led to an urge for alternative sustainable solutions. The use of biopolymers as environmentally friendly materials is one of the potential options. This study aims to investigate the effect of xanthan gum biopolymer as a sustainable solution for soil properties enhancement. The Atterberg limits, unconfined compression, CU and UU triaxial tests were performed to examine the effect of xanthan gum on the soil strength and plasticity. Additionally, the durability of biopolymer-treated and untreated soils under wetting and drying cycles and moisture susceptibility were assessed. The results showed that the compressive strength of soil increased by increasing the xanthan gum concentration and curing time and reached its peak value after a specific curing time. The addition of xanthan gum resulted in significant improvement in soil cohesion and caused a reduction in the internal friction angle of the soil. While increasing the number of wetting/drying cycles decreased the soil strength, the biopolymer-treated soil exhibited higher soil strength than the untreated soil. This study provides valuable experiences in the use of xanthan gum biopolymer in practical engineering applications.

Debris flow mitigation by using biopolymers as a soil stabilizer

Towards rising the attention to the use of green materials in geotechnical applications, this study aims to introduce carrageenan as a new environment-friendly polymer for slope surface stabilization. A set of experiments were conducted to evaluate the performance of the biopolymer-treated soil to form a resistant surface against the surface erosion and debris flow. samples were tested by changing a variety of effective parameters including biopolymer content, moisture content, curing time, soil type, and durability under wet- dry cycles. Kaolinite soil along with river sand in different combinations were employed and treated by various biopolymer proportions to optimize the biopolymer and soil parameters. Subsequently, the optimum mixture of each biopolymer-treated soil was subjected to 5 cycles of wetting and drying. A broad microstructural study by performing FTIR analysis and scanning electron microscopy (SEM) images was conducted and an analytical model was developed to clarify how biopolymer stabilize the slope surface. The results confirm the successful performance of carrageenan in connecting soil grains, increasing mechanical strength and durability of soil against surface erosion. It can be concluded that carrageenan can be considered as a sustainable alternative to conventional materials such as cement and lime.

Durability and strength degradation of xanthan gum based biopolymer treated soil subjected to severe weathering cycles

Biopolymer-based soil treatments have shown effectiveness in soil improvement, with successful field-scale implementation. In this study, we explored the effect of cyclic wetting–drying (W–D) and freezing–thawing (F–T) on the strength durability of biopolymer-treated soils. The results indicate that cyclic W–D and F–T gradually degrade soil strength owing to water adsorption and local biopolymer dilution. Poorly graded sand was highly vulnerable to these weathering effects; however, this problem was mitigated when the soil contained a fines content of 15–25%. These biopolymer-treated soils effectively resisted numerous cycles of both W–D and F–T, indicating that biopolymer-treated soils are suitable for earthen slope reinforcement.

Durability against Wetting-Drying Cycles of Sustainable Biopolymer-Treated Soil.

The world today is more oriented towards sustainable and environmental-friendly solutions in every field of science, technology, and engineering. Therefore, novel sustainable and eco-friendly approaches for soil improvement have also emerged. One of the effective, promising, and green solutions is the utilization of biopolymers. However, even though the biopolymers proved to be effective in enhancing the soil-mechanical properties, it is still unknown how they behave under real environmental conditions, such as fluctuating temperatures, moisture, plants, microorganisms, to name a few. The main research aim is to investigate the durability of biopolymer-improved soil on the cyclic processes of wetting and drying. Two types of biopolymers (Xanthan Gum and Guar Gum), and two types of soils (clean sand and silty sand) were investigated in this study. The results indicated that some biopolymer-amended specimens kept more than 70% of their original mass during wetting-drying cycles. During the compressive strength analysis, some biopolymer-treated specimens kept up to 45% of their initial strength during seven wetting-drying cycles. Furthermore, this study showed that certain damaged soil-biopolymer bonds could be restored with proper treatment. Repeating the process of wetting and drying can reactivate the bonding properties of biopolymers, which amends the broken bonds in soil. The regenerative property of biopolymers is an important feature that should not be neglected. It gives a clearer picture of the biopolymer utilization and makes it a good option for rapid temporary construction or long-standing construction in the areas with an arid climate.

Mechanical and biodeterioration behaviours of a clayey soil strengthened with combined carrageenan and casein

In the last decade, biopolymers have been used as organic soil binders in ground improvement and earthen construction material modification. Although biopolymer-treated soils have substantially enhanced mechanical strength, the deformation characteristics under external loads and material durability (e.g. biodeterioration due to microbial activity) have not yet been fully understood, which limits the in situ practical application of the biopolymer-based soil treatment technology. This study investigated the efficiency of combined carrageenan and casein in strengthening a clayey soil with the biodeterioration consideration. Both mechanical tests (e.g. unconfined compressive strength and one-dimensional consolidation) and biological tests (e.g. high throughput sequencing and rating of mould growth) were conducted. Results indicated that the usage of the carrageenan–casein mixture induced a higher soil compressive strength compared with either carrageen or casein, due to the formation of a three-dimensional gel network. In addition, carrageenan–casein mixture and casein decreased the compressibility of the clayey soil, which might be attributed to the casein’s peculiarity of self-associating into micelles, leading to minimal interactions with water molecules. Carrageenan, due to its affinity for water, increased the soil compressibility. Under the impact of microbial activity, the biopolymer-treated soils underwent deterioration in both surface appearance (i.e. coloured stains and patches caused by mould growth) and compressive strength. A linear relationship was proposed, in which a reduction in compressive strength by approximately 11% is expected while the rating of mould growth is increased by one in a five-rating system. The current research demonstrates that the soil reinforcement with combined carrageenan and casein is able to improve both soil strength and deformation behaviours. It is also suggested to take into account the biodeterioration considerations in the design and implementation of biopolymer-based soil reinforcement practices.

Macroscopic Stress-Strain Response and Strain-Localization Behavior of Biopolymer-Treated Soil.

The enhancement of soil engineering properties with biopolymers has been shown recently as a viable and environmentally benign alternative to cement and chemical stabilization. Interest in biopolymer-treated soil is evident from the upsurge of related research activities in the last five years, most of which have been experimental in nature. However, biopolymers have not yet found their way into engineering practice. One of the reasons for this may be the absence of computational models that would allow engineers to incorporate biopolymer-treated soil into their designs. Therefore, the main goal of this study is to numerically capture a macroscopic stress-strain response and investigate the effect of biopolymers on the onset of strain localization. Several diagnostic strain-localization analyses were conducted, thus providing strain and stress levels at the onset of strain localization, along with the orientations of the deformation band. Several unconfined compression and triaxial tests on the plain and biopolymer-treated soils were modeled. Results showed that biopolymers significantly improved the mechanical behavior of the soil and affected the onset of strain localization. The numerical results were confirmed by the digital image analysis of the unconfined compression tests. Digital image processing successfully captured high strain concentrations, which tended to occur close to the peak stress.

Effect of Biopolymeric Stabilization on the Strength and Compressibility Characteristics of Cohesive Soil

Sustainable engineering discourages the use of conventional soil stabilizers such as lime and cement owing to their higher carbon emission rates. To address these challenges, many researchers considered biopolymer stabilization, a promising green technique in geotechnical engineering practice for treating expansive soils. This study evaluated the performance of two biopolymers, xanthan gum (XG) and guar gum (GG), in improving the unconfined compressive strength (UCS) and consolidation characteristics of an expansive soil subjected to different testing conditions. The dosage of the biopolymers (XG and GG) was maintained at 0.5%, 1%, 2%, and 4% by weight of dry mass of soil mass. Biopolymer treated samples were subjected to desiccator and natural curing conditions (i.e., specimens were exposed to different temperature and relative humidity conditions) for 7, 14, 28, 45, and 60 days. Results showed that the UCS of biopolymer-treated soil increased with increased dosage up to 2% and 1% for XG and GG, respectively; strength significantly improved during the first 28 days of curing under controlled conditions. Improvement of strength was due to increased adhesive strength between gum strands and soil particles. One-dimensional fixed-ring oedometer consolidation test results indicated that the compressibility and swelling characteristics of biopolymer-treated soil increased due to the hydrophilic nature of gum and an increase in the repulsive forces between negatively charged clay particles and the respective functional groups of XG and GG. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were performed on both untreated and biopolymer-treated soil to evaluate the interaction mechanism between soil and biopolymer strands. The microlevel studies confirmed the crosslinking of soil particles by gum strands, which aids in the strength improvement.