Search Results (47)

Soil improvement is one of the fundamental practices in civil engineering, with a long-standing history. In today’s context, the rapidly increasing demand for construction driven by urbanization has further emphasized the necessity and significance of soil stabilization techniques. This study aims to determine the optimum parameters for improving sandy soils by incorporating sodium alginate (SA) as a biopolymer additive into the microbial calcium carbonate precipitation (MICP) process. Sand types S1, S2, and S3, each with distinct particle size distributions, were selected, and the specimens were prepared at medium relative density. Three distinct approaches, MICP, SA, and MICP + SA, were tested for comparison. Additionally, two different improvement methods, injection and mixing, were applied to investigate their effects on the geotechnical properties of the soils. In this context, hydraulic conductivity, unconfined compressive strength (UCS), and calcite content tests, as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses, were performed to assess the changes in soil behavior. SA contributed positively to the overall efficiency of the MICP process. The study highlights SA-assisted MICP as an alternative that enhances the microstructural integrity of treated soils and responds to the environmental limitations of conventional methods through sustainable innovation. Full article

Biopolymers, owing to their environmentally friendly and sustainable characteristics, have become a promising alternative for soil stabilization in geotechnical engineering. The application of protein-based biopolymers as binders for soil stabilization is less prevalent in geotechnical engineering compared to polysaccharide-based biopolymers. This study explores the potential of gelatin, a protein-based biopolymer derived from animal collagen, for stabilizing silty sand and improving its geotechnical properties. Gelatin was mixed into the soil at concentrations ranging from 0.25% to 2% of the dry weight of soil, and its effects on various soil characteristics were evaluated. The tests conducted include liquid limit, plastic limit, compaction behavior, and unconfined compressive strength (UCS); the addition of 1% gelatin led to an approximate 1.69 times increase in the strength of the unamended soil. After 28 days of curing, the UCS improved by approximately 5.03 times compared to the untreated soil, and the treated soil exhibited increased resistance to deformation under load. Microstructural analysis using scanning electron microscopy (SEM) revealed that gelatin facilitated the formation of a cohesive matrix, enhancing particle bonding and reducing void spaces within the soil. Carbon footprint analysis (CFA) conducted on an isolated footing stabilized with gelatin showed that the carbon emissions were reduced by 99.8% and 99% compared to traditional stabilizers such as lime and cement. Additionally, the interaction between the biopolymer and the fine-grained soil is distinctly evident in the FTIR and XRD analysis through hydrogen bonding and the formation of cementitious compounds. Full article

The emphasis on sustainable and environmentally friendly practices in geotechnical engineering has generated interest in alternative soil stabilizing techniques. The present study examines the application of xanthan gum (XG) and guar gum (GG) to enhance the strength of a sand–bentonite composite and explore their potential for use as landfill liners or impervious barriers. The mixtures, consisting of 25% bentonite and 75% sand, were treated with XG and GG concentrations of different percentages (0.5%, 1%, 2%, and 3% by dry mass). The test results indicated that a 2% addition was optimal for both biopolymers. Using this optimum value of XG and GG significantly increased the unconfined compressive strength (UCS) by almost 3-fold compared to the strength of untreated samples. Meanwhile, XG demonstrated a slightly higher impact on strength attributed to its robust gel-forming and binding properties. Comparisons between the two biopolymers highlighted XG’s superior performance, with UCS improvements of up to 20% over GG-treated samples. These results underscore the potential of biopolymers as effective, sustainable alternatives to traditional stabilizers, providing both mechanical enhancements and environmental benefits. The present study contributes valuable insights into green soil stabilization techniques, supporting the development of more sustainable construction practices. Fourier Transform Infrared Spectroscopy (FTIR) was conducted to analyze the chemical interactions between sand–bentonite mixtures and biopolymers, which possibly provide insights into the bonding mechanisms responsible for the observed improvements in mechanical and volumetric behavior. Full article

Soft soil poses significant challenges in highway engineering due to its low strength and high compressibility. This study proposes using xanthan gum biopolymer as an environmentally friendly agent to improve the mechanical behavior of soft soil. Laboratory tests were conducted to analyze the unconfined compressive strength (UCS) and compressibility of xanthan-gum-stabilized soft soil under dry–wet cycles. Physicochemical analysis was performed to examine the pH value, electrical conductivity, and total dissolved solids (TDS) of the stabilized soil. Additionally, microscopic tests were performed to investigate the stabilization mechanism. The results demonstrate that the UCS of the stabilized soil consistently increases with curing age while it decreases under dry–wet cycles. Moreover, the UCS, durability, and modulus of compressibility of the stabilized soil initially increase significantly and then slightly decrease with increasing xanthan gum dosage. At the optimal xanthan gum dosage (1.5%), the UCS reaches 376.3 kPa at 28 d of curing and drops by only 24.1% even after ten dry–wet cycles, and the modulus of compressibility is enhanced to 37.13 MPa; meanwhile, the corresponding compression index and coefficient of compressibility are reduced to 0.082 and 0.061 MPa⁻¹, respectively, indicating satisfactory performance of the stabilized soil as highway foundation material. The stabilization mechanism of xanthan-gum-treated soft soil primarily involves the bonding and filling effects of the hydrogel resulting from the hydration of xanthan gum. These findings suggest that xanthan gum is a promising and effective stabilizing agent for soft soil as it can significantly reduce soil water content and void ratio. Full article

In response to the need for sustainable soil stabilization alternatives, this study explores the use of waste materials and biopolymers to improve the mechanical behavior of clay from Cartagena, Colombia. Crushed limestone waste (CLW), ground glass powder (GG), recycled gypsum (GY), xanthan gum (XG), and the combination of XG with polypropylene fibers (XG–PPF) were used as stabilizing agents. Samples were compacted at different dry densities and cured for 28 days. Unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were conducted to assess the strength and stiffness of the treated mixtures. Results were normalized using the porosity/binder index ($\mathrm{\eta }/B_{iv}$), leading to predictive equations with high determination coefficients (R² = 0.94 for UCS and R² = 0.96 for stiffness). However, XG-treated mixtures exhibited distinct behavior that prevented their inclusion in a unified predictive model, as the fitted exponent x in the porosity/binder index ($\mathrm{\eta }/B_{iv}^x$) differed markedly from the others. While an exponent of 0.28 was suitable for blends with mineral binders, the optimal x values for XG and XG–PPF mixtures were significantly lower at 0.02 and 0.03, respectively, reflecting their unique gel-like and fiber-reinforced characteristics. The analysis of variance (ANOVA) identified cement content and compaction density as the most influential factors, while some interactions involving the residues were not statistically significant, despite aligning with experimental trends. The findings support the technical viability of using sustainable additives to enhance soil properties with reduced environmental impact. Full article

Granite residual soil exhibits a tendency to collapse and disintegrate upon exposure to water, displaying highly unstable mechanical properties. This makes it susceptible to landslides, mudslides, and other geological hazards. In this study, three common biopolymers, i.e., xanthan gum (XG), locust bean gum (LBG), and guar gum (GG), are employed to improve the strength and stability of granite residual soil. A series of experiments were conducted on biopolymer-modified granite residual soil, varying the types of biopolymers, their concentrations, and curing times, to examine their effects on the soil’s strength properties and failure characteristics. The microscopic structure and interaction mechanisms between the soil and biopolymers were analyzed using scanning electron microscopy and X-ray diffraction. The results indicate that guar gum-treated granite residual soil exhibited the highest unconfined compressive strength and shear strength. After adding 2.0% guar gum, the unconfined compressive strength and shear strength of the modified soil are 1.6 times and 1.58 times that of the untreated granite residual soil, respectively. Optimal strength improvements were observed when the biopolymer concentration ranged from 1.5% to 2%, with a curing time of 14 days. After treatment with xanthan gum, locust bean gum, and guar gum, the cohesion of the soil is 1.36 times, 1.34 times, and 1.55 times that of the untreated soil, respectively. The biopolymers enhanced soil bonding through cross-linking, thereby improving the soil’s mechanical properties. The gel-like substances formed by the reaction of biopolymers with water adhered to encapsulated soil particles, significantly altering the soil’s deformation behavior, toughness, and failure modes. Furthermore, interactions between soil minerals and functional groups of the biopolymers contributed to further enhancement of the soil’s mechanical properties. This study demonstrates the feasibility of using biopolymers to improve granite residual soil, offering theoretical insights into the underlying microscopic mechanisms that govern this improvement. Full article

Low-plasticity silts (ML) found in Metro Manila, Philippines, characterized by low strength, stiffness, and bearing capacity, often require stabilization. Traditional methods using cement are associated with significant carbon emissions, causing environmental concerns. Sustainable materials such as agar biopolymers can be an alternative to cement to improve the strength of fine-grained soils. A comparative study was conducted on ML samples treated with agar and cement at different concentrations (1%, 3%, 5%, and 7%) and subjected to varying curing periods (7, 21, 28, and 35 days) under air-dried conditions using Unconfined Compressive Strength (UCS) tests. Agar-treated samples generally exhibited higher UCS values than cement-treated samples across the tested concentrations and curing periods. Samples with 3% and 5% agar were significantly stronger than their cement-treated counterparts. The strength of agar-treated soils peaked at a 5% concentration and subsequently decreased at 7% agar, possibly due to a masking effect. SEM-EDS analysis revealed that a 5% agar concentration achieved a balanced microstructure with effective particle bonding, while higher concentrations led to diminished strength due to reduced mechanical interlocking from excessive biopolymer coverage. Subsequent statistical analysis also indicated significant improvement using agar versus cement-treated and untreated soils, especially at 5% agar. A predictive polynomial regression model demonstrated the influence of curing days and agar concentration on UCS, attaining R² = 0.94 vs. experimental values. Using agar biopolymers presents a promising and potentially more sustainable approach to soil, highlighting the potential of utilizing a locally abundant resource for geotechnical engineering applications. Full article

Civil and geotechnical researchers are searching for economical alternatives to replace traditional soil stabilizers such as cement, which have negative impacts on the environment. Chitosan biopolymer has shown its capacity to efficiently minimize soil erosion, reduce hydraulic conductivity, and adsorb heavy metals in soil that is contaminated. This research used unconfined compression strength (UCS) to investigate the impact of chitosan content, long-term strength assessment, acid concentration, and temperature on the improvement of soil strength. Static triaxial testing was employed to evaluate the shear strength of the treated soil. Overall, the goal was to identify the optimum values for the mentioned variables so that the highest potential for chitosan-treated soil can be obtained and applied in future research as well as large-scale applications in geotechnical engineering. The UCS results show that chitosan increased soil strength over time and at high temperatures. Depending on the soil type, a curing temperature between 45 to 65 °C can be considered optimal. Chitosan biopolymer is not soluble in water, and an acid solution is needed to dissolve the biopolymer. Different ranges of acid solution were investigated to find the appropriate amount. The strength of the treated soil increased when the acid concentration reached its optimal level, which is 0.5–1%. A detailed chemical model was developed to express how acid concentration and temperature affect the properties of the biopolymer-treated soil. The SEM examination findings demonstrate that chitosan efficiently covered the soil particles and filled the void spaces. The soil was strengthened by the formation of hydrogen bonds and electrostatic interactions with the soil particles. Full article

For almost a decade, various studies have been carried out to prove the suitability of nano additives in enhancing the geotechnical properties of soil. Yet, this line of research is still in its elementary stage, restricting itself to laboratory tests to determine soil’s index and engineering properties blended with varying dosages of nano additives. In other words, research on practical applications of nano additives for soil stabilization is scarce. The present work attempts to investigate the suitability of three different nanomaterials as a load-bearing stratum for shallow foundations. The nano additives were chosen in such a way that each of them is from a different origin. One of them is nano calcium carbonate (inorganic) whereas the other two are nano-sized varieties of natural biopolymers, namely nano chitosan (crustacean-based) and nano carboxymethyl cellulose (plant-based). A series of laboratory tests were initially conducted to determine the strength of all three nano-additive-treated soils at different dosages, which were investigated for 180 days to ensure their long-term performance. This was followed by a foundation model study on untreated soil and on soil treated with optimal dosages of nano additives. The results were validated using finite element software followed by a parametric study to optimize the depth of soil stabilization. It was observed that all three nano additives exhibited a better performance when the top layer had the optimal dosage and the subsequent layers had a relatively lesser dosage. Full article

The application of biopolymers for sand stabilization has recently gained attention due to their natural composition, which makes them both environmentally friendly and of reasonable cost. Measuring the soil–water retention curve (SWRC) of biopolymers-treated sand is essential for the design, modeling, and interpretation of the unsaturated behavior of these materials. Unsaturated shear strength, unsaturated flow, and associated retention capacity are well addressed and evaluated using SWRC. Therefore, this study examined the possible effects of biopolymers—sodium alginate (SA), guar gum (GG), and pectin (P) on the SWRC and retention capacity for stabilized sand. Apart from natural sand, three different concentrations were investigated for each biopolymer. The SWRCs were measured over the entire practical range of suction using a combination of three techniques: hanging column for low suction measurement, axis translation techniques for moderate suction measurement, and vapor equilibrium technique for high suction measurement. The results indicate significant changes in SWRC, and a new series of micropores was developed, this, in turn, extends the desaturation zone of treated sand from a low suction range (i.e., 30 kPa) to moderate to high suction levels (i.e., 10,000 kPa). The saturated water content (w_s) was slightly reduced, air entry values (AEVs), and residual suction (s_r) significantly increased and multiplied up to 200 and 75 times respectively. The retention capacity increased, exhibiting a dependency between the biopolymer type and suction range. The results are of great significance for both practitioner engineers and researchers in predicting the unsaturated soil functions of treated sand. Full article

This paper found that environmentally friendly guar gum biopolymers are helpful for stopping the erosion of basalt residual-soil shallow slopes, while also improving the problems of poor stability, difficult growth of early vegetation, and weak initial resistance to the rainfall scouring of these slopes under extreme climatic conditions. Then, to illustrate the effects of the guar gum treatment, laboratory tests have been conducted, including a soil strength test, water retention and water absorption tests, a disintegration test, and a simulated rainfall erosion test, and the pattern of its effect on vegetation growth has been explored. The results indicate that as the content of guar gum increases, both the cohesion and angle of internal friction exhibit a trend of first increasing and then decreasing; the angle of internal friction varies within a range of 21° to 26°. The evaporation rate, water absorption rate, and disintegration rate of this guar gum-treated soil were significantly reduced, while the cracking of the surface layer was significantly improved. The disintegration rate of the soil is only about 2%, as the guar gum content is greater than 1%. Moreover, there is no sign indicating that vegetation germination was affected by the guar gum, meaning that it maintains a favorable environment for vegetation to grow. Guar gum-cured slopes were significantly protected under heavy rainfall washout conditions, with a 94.85% reduction in total soil loss from the slope surface compared to untreated slopes. Since the pores of soil are filled with guar gum hydrogel, the erosion resistance of soil is greatly enhanced. The results of this study will provide a scientific basis for engineering the protection of shallow slopes of basalt residual soils. Full article

Using biopolymers for soil stabilization is favorable compared to more conventional methods because they are more environmentally friendly, cost-effective, and long-lasting. This study analyzes the physical properties of guar gum and laterite soil mixes. A comprehensive engineering study of guar gum-treated soil was conducted with the help of a brief experimental program. This study examined the effects of soil–guar gum interactions on the strengthening behavior of guar gum-treated soil mixtures using a series of laboratory tests. The treated laterite soil’s dry density increased marginally, while its optimum moisture content decreased as the guar gum increased. Treatment with guar gum significantly enhanced the strength of laterite soil mixtures. For laterite soil with 2% guar gum, the unsoaked CBR increased by 148% and the soaked CBR increased by 192.36%. The cohesiveness and internal friction angle increased by 93.33% and 31.52%, respectively. These results show that using guar gum dramatically improves the strength of laterite soil, offering a more environmentally friendly and sustainable alternative to traditional soil additives. Using guar gum in T8 subgrade soil requires a 1395 mm pavement depth and costs INR 3.83 crores, 1.52 times more than laterite soil. For T9 subgrade soil, the depth was 1495 mm, costing INR 4.42 crores, 1.72 times more than laterite soil. This study introduces a novel approach to soil stabilization by employing guar gum, a biopolymer, to enhance the physical and mechanical properties of laterite soil. Furthermore, this study provides a detailed cost–benefit analysis for pavement applications, revealing the financial feasibility of using guar gum despite it requiring a marginally higher initial investment. Full article

Biopolymers have been widely experimented with as organic stabilizers in the last decade for improving soil properties. However, the high nutritional value of some biopolymers like chitin, carrageenan, casein, and chitosan can also promote microbial growth which can affect the improvement in the strength of biopolymer-stabilized soil. This study investigates the mechanical behaviour of clay treated with chitosan at dosages of 0.5, 1.0, 1.5, and 2.0% at various curing periods of 7 d, 28 d, 56 d, and 90 d and also observes the fungal growth, the conditions favourable to fungal growth, and the effect of an inorganic secondary additive on the mechanical behaviour of treated soil. The study shows that fungal growth is higher with the time and dosage of chitosan. The strength of chitosan-treated samples increased with both dosage and age despite the fungal growth observed on the treated soil, as did the fungal growth. On treating the soil with 2% chitosan, the percentage increase in strength was nearly 14.39%, and on the 56th day, it was phenomenally increased to 1534.39%. In an attempt to control the fungal growth, a secondary additive, calcium metasilicate (calsil), was added to various dosages of chitosan-treated soil (CTS). The secondary additive did not completely stop the fungal growth but certainly controlled fungal growth. Chitosan and calsil are hydrophilic, increasing OMC by 67% and 150% for the high CTS and calsil–chitosan-treated soil (CCTS) doses. Calsil coated the soil particles and prevented closer packing under compaction, reducing MDUW by 7.8% and 18% for CTS and CCTS at maximal dosage. The development of hydrated cementitious products made the soil brittle, causing the post-peak strength of CCTS samples to diminish significantly with age. FTIR spectroscopy showed hydrogen bonding strengthening CTS, while XRD revealed cementitious compounds in CCTS. The strength of the soil treated with chitosan and calsil showed a higher strength than soil treated with only chitosan. Full article

Biopolymers are polymers of natural origin and are environmentally friendly, carbon neutral and less energy-intense additives that can be used for various geotechnical applications. Biopolymers like xanthan gum, carrageenan, chitosan, agar, gellan gum and gelatin have shown potential for improving subgrade strength, erosion resistance, and as canal liners and in slope stabilization. But minimal research has been carried out on cellulose-based biopolymers, particularly microcrystalline cellulose (MCC), for their application in geotechnical and geo-environmental engineering. In this study, the effect of MCC on select geotechnical properties of kaolin, a weak, highly compressible clay soil, like its liquid and plastic limits, compaction behavior, deformation behavior, unconfined compression strength (UCS) and aging, was investigated. MCC was used in dosages of 0.5, 1.0, 1.5 and 2% of the dry weight of the soil, and the dry mixing method was adopted for sample preparation. The results show that the liquid limit increased marginally by 11% but the plasticity index was nearly 74% higher than that of untreated kaolin. MCC rendered the treated soil stiffer, which is reflected in the deformation modulus, which increased with both dosage and age of the treated sample. The UCS of kaolin increased with dosage and curing period. The maximum UCS was observed for a dosage of 2% MCC at a 90-day curing period. The increase in stiffness and strength of the treated kaolin with aging points out that MCC can be a potential soil stabilizer. Full article

Biopolymer stabilization of soils has emerged as a viable solution for enhancing the engineering properties of soils in recent years. Xanthan gum and guar gum are two commonly used biopolymers. When combined, these materials have the ability to create stronger gels or gel strengths comparable to those achieved by using xanthan or guar gum individually, but at lower total concentrations. However, the extent of this synergistic viscosity-enhancing effect on soil improvement remains unclear. This study analyzes the effects of xanthan gum and guar gum on the physical and mechanical properties of clay under both individual and combined conditions using Atterberg limits tests, compaction tests, and triaxial consolidation undrained tests. At a 2% biopolymer content, the liquid limit of clay treated with a combination of XG and GG compounds increases by up to 8.0%, while the plastic limit increases by up to 3.9% compared to clay treated with a single colloid. With an increase in the mixing ratio, the optimal water content initially rises and then declines, peaking at 27.3%. The maximum dry density follows a pattern of initially decreasing and then increasing, with the lowest value recorded at 1.616 g·cm⁻³. Moreover, the shear strength of specimens treated with the XG and GG combination generally surpasses that of specimens treated with XG or GG alone. Furthermore, the combined treatment results in increased plasticity, highlighting its potential to enhance safety and stability in engineering applications. Full article