This study explores the effectiveness of soft viscoelastic biopolymer inclusions in mitigating cyclic liquefaction in loosely packed sands. This examination employs cyclic direct simple shear testing (CDSS) on loose sand treated with gelatin while varying the gelatin concentration and the cyclic stress ratio (CSR). The test results reveal that the inclusion of soft, viscoelastic gelatin significantly reduces shear strain and excess pore pressure during cyclic shear. Liquefaction potential, defined as the number of cycles to liquefaction (NL) at an excess pore pressure ratio (ru = Delta u/sigma ' vo) of 0.7, is substantially improved in gelatin-treated sands compared to gelatin-free sands. This improvement in liquefaction resistance is more pronounced as the inclusion stiffness increases. Furthermore, the viscoelastic pore-filling inclusion helps maintain skeletal stiffness during cyclic shearing, resulting in a higher shear modulus in gelatin-treated sand in both small and large-strain regimes. At a grain scale, pore-filling viscoelastic biopolymers provide structural support to the skeletal frame of a loosely packed sand. This pore filler mitigates volume contraction and helps maintain the effective stress of the soil structure, thereby reducing liquefaction potential under cyclic shearing. These findings underscore the potential of viscoelastic biopolymers as bio-grout agents to reduce liquefaction risk in loose sands.

Conventional in-situ light non-aqueous phase liquid (LNAPL) remediation techniques often face challenges of high costs and limited efficiency, leaving residual hydrocarbons trapped in soil pores. This study investigates the efficiency of an alcohol-in-biopolymer emulsion for enhancing diesel-contaminated soil remediation. The emulsion, formulated with xanthan gum biopolymer, sodium dodecyl sulfate surfactant, and the oil-soluble alcohol 1-pentanol, was evaluated through rheological tests, interfacial tension measurements, and onedimensional sand-column experiments under direct injection and post-waterflooding scenarios. The emulsion exhibited non-Newtonian shear-thinning behavior with high viscosity, ensuring stable propagation and efficient delivery of 1-pentanol to mobilize trapped diesel ganglia. It achieved 100 % diesel recovery within 1.2 PV during direct injection, outperforming shear-thinning polymer-only and polymer-surfactant solutions, which achieved recovery factors of 83.4-92.9 %. Post-waterflooding experiments also demonstrated 100 % diesel recovery within 1.3 PV, regardless of initial diesel saturation. Key mechanisms include reduced interfacial tension, diesel swelling and mobilization induced by 1-pentanol, and uniform displacement facilitated by the emulsion's viscosity. Additionally, the emulsion required lower injection pressures compared to more viscous alternatives, enhancing its injectability into the soil and reducing energy demands. These findings highlight the emulsion's potential to overcome conventional remediation limitations, offering a highly effective and sustainable solution for diesel-contaminated soils and groundwater.

The treatment of soil with biopolymers has demonstrated various benefits, including strength enhancement, reduction in the permeability coefficient, and promotion of vegetation. Consequently, numerous experiments have been conducted to evaluate the strength of biopolymer-treated soils. This study aims to evaluate the interparticle bonding strength attributed to the biopolymer network formed between soil particles, focusing on the strength characteristics at the particle scale. Agar gum, a thermo-gelling biopolymer, was selected to assess the strength of biopolymer solutions. Experiments were conducted at concentrations of 2 %, 4 %, and 6 % with varying drying times to account for the differences in water content. The bonding, tensile, and shear strengths of the agar gum polymer solutions were evaluated under different loading conditions. To compare the strengths and meaningful trends observed in the agar gum polymer solution under different conditions. The results demonstrated that for all strength conditions involving the agar gum solution, the strength increased with higher concentrations and lower water content. During the particle size test, the bonding strength was improved up to 160 kPa, and the tensile strength of the agar gum polymer itself was observed to be up to 351 kPa. Furthermore, the UCS test results of the silica sand mixed with agar gum showed an improvement up to 1419 kPa. Among the evaluated strengths, the tensile strength was the highest, whereas the shear strength was the lowest. A comparison between the adhesive strength tests, which evaluated the strength characteristics at the soil particle scale, and the UCS of silica sand mixed with an agar gum solution revealed a similar trend. The shear strength increased consistently with drying time across all concentration conditions, which was consistent with the trends observed in the UCS. These findings suggest that the strength characteristics of soils treated with agar gum solutions can be effectively predicted and utilized for ground improvement applications.

Eco-friendly materials have gained significant attention for soil stabilization and reinforcement in road construction and geo-environmental infrastructure, as traditional additives pose notable environmental concerns. In this study, three concentrations of Chitosan Biopolymer (CBP) (1.5 %, 3 %, and 4.5 %) as a bio-stabilizer, three proportions of Rice Husk Biochar (RHB) (0.5 %, 1 %, and 1.5 %) as a waste-derived filler, and three dosages of Hemp Fiber (HF) (0.2 %, 0.4 %, and 0.6 %) as reinforcement were used to treat sand-kaolinite mixtures (SKM). The samples were cured for 1, 7, 14, 21, and 28 days and subjected to varying numbers of freeze-thaw (F-T) cycles. A diverse range macro-scale laboratory tests, encompassing compaction, unconfined compressive strength (UCS), indirect tensile strength (ITS), F-T durability, ultrasonic pulse velocity (UPV), and thermal conductivity (TC), were performed on the treated samples. In addition, microstructural analyses using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) were conducted to correlate mechanical behavior with micro- scale properties. The optimal dosages of CBP and RHB were first determined through UCS tests, with 3 % CBP and 1 % RHB proving the most effective. These dosages were then used to analyze their impact on other mechanical properties. Results showed that the compressive and tensile strengths of the bio-stabilized soil at the optimum contents of additives increased by 2410.7 kPa and 201.2 %, respectively, compared to the control samples. Incorporating HF into the SKM-CBP-RHB mixtures significantly enhanced their F-T durability after 10 consecutive cycles, reducing strength deterioration and performance degradation compared to the untreated soil. The optimum composition (3 % CBP, 1 % RHB, and 0.4 % HF) led to a 6.1-fold increase in ITS and a minor 2 % reduction in performance after 10 F-T cycles. Moreover, HF incorporation improved the failure strain and reduced the brittleness of the stabilized soil. UPV and TC tests revealed that incorporating HF at levels up to 0.4 %, combined with the optimum CBP-RHB mixture, enhanced soil stiffness by 963.7 MPa and reduced thermal conductivity by 0.76 W & sdot;m-1 & sdot;K-1. The microstructural analysis confirmed these findings, showing enhanced interlocking between SKM and fibers via hydrogel formation. Overall, the study demonstrates that the CBP-RHB-HF composite markedly enhances soil strength and durability, making these additives highly suitable for applications like landfills, embankments, and slopes.

Currently, the application of enhancement techniques with natural additives for soil stabilization is crucial due to growing urbanization and environmental concerns. Contemporary construction methods increasingly need eco-friendly and cost-effective materials, such as natural fibers. Reinforcing the soil sublayers with fibers improves layer quality and increases its load transfer capacity over a larger surface, thereby reducing the required thickness of upper layers. This study utilized raspberry stalks and xanthan biopolymer as natural additives for the first time to improve the mechanical qualities of bentonite expansive soil. Different tests, including compression and indirect tensile strengths, swelling potential, freeze-thaw (F-T) cycles, California bearing ratio (CBR), and scanning electron microscopy (SEM), were performed on samples comprising 0.2, 0.4, and 0.6 % of raspberry fibers and 0.5, 1, and 2 % of xanthan gum, with curing durations of 1, 7, 14, and 28 days. The test results revealed that the combination of 1 % xanthan and 0.4 % fibers, subjected to 28 days of curing, showed the best performance in increasing the mechanical properties of bentonite. The hydrogel structure and the locks and links formed in the soil by the additives led to increases of 353 % and 103 % in compressive and tensile strengths, respectively. The results also indicated that the free-swelling potential of the unstabilized bentonite soil diminished from 280 % to 74 % when stabilized with optimum percentages of xanthan and fiber. Furthermore, the investigation showed that even after exposure to 10 F-T cycles, the durability of xanthan-fiber-stabilized bentonite soil was significantly higher compared to the unstabilized soil. Moreover, the CBR value of the stabilized soil improved by 143 % compared to the unstabilized soil, indicating a significant increase in soil layer quality. The SEM results verified that the additive combination significantly impacted the strength of the samples. The data indicate that the incorporation of xanthan gum as a bio cohesive agent and raspberry fiber as tensile strands enhances soil strength, hence augmenting the viability of these additives in practical applications, including shallow foundations, adobe brick, and subgrade.

Compacted clays are extensively used as cover barriers to control rainfall infiltration and upward migration of greenhouse gases at municipal solid waste landfills and volatile organic compounds at industrially contaminated sites. Xanthan gum (XG) amendment offers a green and low-carbon solution to improve gas breakthrough pressure and reduce gas permeability of compacted clays, sustainably improve earthen structures. This study aimed to systematically investigate the effects of XG amendment on gas breakthrough pressure, gas permeability, and hydraulic conductivity of compacted clay liners. The gas breakthrough pressure increased from 0.6 kPa to 2.2 kPa (improve similar to 4 times) and the gas permeability decreased from 2.2 x 10(-14) m(2) to 4.8 x 10(-16) m(2) (reduce similar to 200 times) when the XG dosage increased from 0 % to 2 % and apparent degree of saturation was 100 %. Hydraulic conductivity of XG-amended soil at 1 % XG dosage was 2.6 x 10(-10) m/s, which was 3 % of the value measured in unamended soil. Mechanisms of enhanced gas barrier and hydraulic performance were interpreted by the combined effects of (i) soil pore filling substantiated by the analyses of scanning electron microscopy and pore size distribution; (ii) high viscosity of XG hydrogels, validated by the measurement of rheological properties; and (iii) increased diffuse double layer thickness of the amended soils evidenced by the zeta potential analysis.

Global climate change has caused frequent extreme weather events, leading to the degradation of soil engineering properties. Eco-friendly biopolymer has been considered for soil reinforcement under extreme climate. This study investigates the effects of biopolymer amendment on soil mechanical properties under freeze-thaw (F-T) cycles. Direct shear tests were conducted on plain soil (PS) and biopolymer reinforced soil (BRS) under varying water contents (5 %, 15 %, and 25 %) and F-T cycles. Microstructural analysis and numerical simulation were carried out to reveal the influence of biopolymer on the evolutions of microstructure, shear band and particle interaction. The results showed that biopolymer significantly enhanced soil strength, particularly at lower water contents, with strength increases of up to 3.6 times as water content decreased from 25 % to 5 %. BRS exhibited better resistance to strength deterioration under F-T cycles, with an average strength loss of 25.5 % compared to 35 % for PS after 10 cycles. SEM and MIP analyses demonstrated that biopolymer reduced porosity and pore size by filling voids and cementing particles while mitigating F-T damage. DEM simulations revealed that F-T cycles increase the shear band area and reduce the average contact force. However, the addition of biopolymer effectively mitigates the adverse effects of F-T cycles. Biopolymer is demonstrated to be effective in enhancing soil strength and durability in seasonally frozen ground region.

Electronic waste (e-waste) from nonbiodegradable products present a significant global problem due to its toxic nature and substantial environmental impact. In this study novel electrically conductive biodegradable films of uncured natural rubber (NR) incorporating graphite platelets and chitosan were developed via a latex aqueous microdispersion method. Chitosan was added as a dispersing and thickening agent to encourage the uniform distribution of graphite in the NR matrix at loadings of 20-60 parts per hundred rubbers (phr). FTIR confirmed interactions between NR, graphite, and chitosan. FE-SEM and Synchrotron XTM analyses demonstrated uniform graphite dispersion. The result of XRD revealed the greatest crystallinity at 86.9% with 60 phr graphite loading. Mechanical properties testing indicated a significant increase in Young's modulus to 58.2 MPa, or about 470-fold improvement over the pure NR film. The composite films demonstrated improved thermal and chemical resistance, and their electrical conductivity could rise dramatically to 1.22 x 10-5 S cm-1 at 60 phr graphite loading, or about six orders of magnitude higher than pure NR film. The composite films exhibit antibacterial activity against Staphylococcus aureus and some inhibition against Escherichia coli. In addition, the NR composite films exhibited biodegradability ranging from 16.7% to 25.1% after three months of soil burial, declining with increased graphite loading. These results demonstrate the potential of NR-graphite composites as conductive materials for flexible electronics, such as thin-film electrodes in energy storage devices and sensors.

Transforming waste materials into valuable commodities is a promising strategy to alleviate challenges associated with managing solid waste, benefiting both the environment and human well-being. This study is focused towards harnessing the potential of waste eggshell microparticles (ESMP) (0.10, 0.15, 0.20 g/150 mL) as reinforcing biofiller and orange peel essential oil (OPEO) (14 %, 25 % and 36 %, w/w) as bioactive agent with pectin (2.80, 2.85, 2.90, and 3.00 g/150 mL) to fabricate five different biocomposite films using particle dispersion and solvent casting technique. The addition of ESMP and OPEO progressively increased film thickness and led to variations in transparency. Micromorphological analysis and vibrational spectroscopy indicated hydrophobicity and compactness, as showed by the loss of free O- H bonds, sharpening of aliphatic C- H and stretching of C = C, C- O and C- O- C bonds with increasing filler content. Noticeable improvements in thermal stability and tensile strength were observed, while the flexibility was minimized. The films displayed remarkable barrier properties against hydrological stress, as evidenced by a reduction in water activity, moisture content, water uptake capacity, and solubility. The antioxidant activity against DPPH radicals suggested efficient release of bioactive compounds. Antibacterial assessment revealed inhibitory effect on Staphylococcus aureus and Bacillus cereus. During soil burial, notable weight loss along with shrinkage confirmed the film biodegradability. In conclusion, the pectin-ESMP-OPEO biocomposite films show potential characteristics as food packaging materials, warranting further performance testing on food samples.

Earth-building materials offer a low-carbon option for construction, but their poor water resistance limits their adoption by the construction industry. Adding biopolymers to earth materials can improve mechanical strength and water resistance but also promote mold mycelium growth that reduces indoor air quality. However, for other applications such as insulation or packaging, the controlled growth of specific mycelium is seen as a promising option for producing natural waterproof materials. These application require heat-inactivation to kill the mycelium and preserve air quality. It is currently unknown if heat-inactivated mold mycelium could improve the water resistance of earth materials. This study explores a new design by promoting the natural growth of molds on biostabilized earth materials and studying the effect on earth material properties after heat inactivation. Earth mortars were prepared by mixing soil, water, and biopolymers (2 % of soil mass) to a consistent texture. Twenty formulations, using two soils and four biopolymers, were subjected to two different 21-day cures, under dry (oven at 50 degrees C) or humid (30 degrees C, 98 % RH) conditions. Mortar properties were investigated after a 48-h 80 degrees C heat treatment to inactivate mold. We found that the humid cure consistently prompted mold growth on biostabilized mortars, which was associated with significantly higher water resistance compared to unexposed mortars. Specifically, capillary water absorption and mass loss after water spray was reduced by 28 % and 64 % respectively. These improvements were achieved with minimal impact on shrinkage, density, and mechanical strength. The amelioration in water resistance was attributed to the hydrophobic mold mycelium filling the earth mortar pore as observed by UV microscopy. Together, this study demonstrates that mycelium could dramatically improve the water resistance of biostabilized earth materials.