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.

This paper assesses the performance of biopolymers (agar gum and guar gum) for soil stabilization and the self-healing properties of these materials using non-destructive ultrasonic pulse velocity (UPV) and unconfined compressive strength (UCS) tests. Scanning electron microscopy (SEM) tests were performed to investigate the microstructure of the stabilized soil during the self-healing process. The results showed that adding biopolymers to the soil significantly improved the soil's mechanical properties and self-healing properties. The self-healing indexes of sandy soil stabilized with 1% of guar gum and agar gum were 45% and 18%, respectively, at the curing time of 14 days. Increasing the internal bonds and reducing cracking caused by hydrogel swelling are the significant advantages of using biopolymers in soil stabilization. The UPV provides a quick and accurate estimate of changes in the properties of the stabilized soil. The UPV of the samples increased after the self-healing period. The UPV of the sandy soil stabilized with 1% guar gum and agar gum increased by 17% and 13%, respectively, at the curing time of 7 days. The SEM results showed that the swelling of biopolymers led to crack repair after the self-healing period, the creation of new bonds between grains, and the increase of the contact surface of soil particles.

This study investigates the geotechnical performance of municipal solid waste fines (MSWF) stabilized with xanthan gum and agar gum. As urbanization escalates, the challenge of managing MSW becomes more critical, especially in India, projected to produce up to 436 million tonnes annually by 2050. Landfill mining yields material with poor engineering properties, necessitating effective stabilization techniques. This research evaluates the efficacy of xanthan and agar gums in enhancing the geotechnical properties of MSW fines. Various tests, including compaction, triaxial, and unconfined compressive strength, were conducted on samples subjected to different curing periods. The results indicate a substantial improvement in the mechanical properties of MSW fines treated with agar gum, including a maximum increase of 58% in unconfined compressive strength (UCS). Microstructural examinations confirm enhanced interparticle bonding, while leachate analysis shows a notable reduction in heavy metal release. Statistical assessments underscore the significance of curing time in determining the final properties of the treated MSW fines. Overall, agar gum emerges as a more effective biopolymer for MSW fines stabilization, with curing duration playing a vital role in achieving optimal geotechnical characteristics. These findings offer valuable insights for selecting appropriate bio-treatment methods for heterogeneous materials like MSW fines.

Liquefaction can cause ground subsidence and structural collapses, which could result in considerable damage. While numerous preventive methods have been proposed to prevent such liquefaction, most of these methods involve cement-based reinforcements, thus potentially introducing other environmental problems, such as groundwater contamination and increased carbon dioxide emissions. Therefore, it is essential to develop and use eco-friendly, ground-reinforcement materials. Agar gum is an eco-friendly biopolymer extracted as a result of the biological activities of microorganisms. Ground-reinforcement of agar gum enhances its effectiveness in improving the unconfined compressive and shear strengths, thus making it a suitable, eco-friendly, ground-reinforcement material. However, while the use of agar gum could (logically) increase the strength of lique-faction resistance, there is insufficient research to support this assumption. Therefore, in this study, the viscosity, unconfined compressive strength, and hardness of agar gum were quantified, and the liquefaction resistance strength was evaluated based on cyclic triaxial tests using agar-gum-treated samples. The hardness, unconfined compressive strength, and liquefaction resistance strength increased with increasing agar gum concentrations, and the change based on a curing time was relatively constant. In addition, the effect of enhancing the lique-faction resistance strength using agar gum was confirmed based on a comparison with previous studies using untreated samples and other reinforcing materials.