Expanding on the challenges of expansive soils to civil infrastructure, this research delves into the synergistic application of microbially induced calcium carbonate precipitation (MICP) through bio-stimulation and natural fiber reinforcement to mitigate soil swell-shrink behavior and enhance soil strength. This research diverges from traditional methods by addressing their economic and environmental limitations. The dual strategy of bio-stimulation with natural fiber reinforcement was assessed through laboratory tests, including unconfined compression, 1D swell, linear shrinkage tests, and microstructural analysis. This methodology involved preparing solutions to foster bacterial growth and strategically adding jute fibers to enhance the soil matrix. Results revealed significant improvements in soil strength (up to 186%), and reductions in swell strain (up to 85%) and swell pressure (up to 90%), with the optimal jute fiber content at 1.5%. Additionally, a significant increase in calcium carbonate content (163-176%) highlighted bio-stimulation's role in soil stabilization. SEM analysis showed that bio-stimulation and jute fiber reinforcement transformed the soil microstructure, enhancing cohesion and reducing deformability. These outcomes highlight the promise of combining bio-stimulated MICP with natural fiber reinforcement as an eco-friendly and efficient approach to soil stabilization. They also add to the growing body of knowledge on tackling the issues posed by expansive soils in civil engineering applications.

A few recent studies introduced natural rubber latex (NRL) as a stabilizer for improving the mechanical properties of soil such as ductility, compressive and tensile strengths, durability, etc. However, none of these studies addressed the effect of NRL treatment on swelling and compressibility of soil. The present study investigates the effect of NRL treatment on swelling and compressibility characteristics of three soils of different plasticities by conducting oedometer tests. Untreated and NRL-treated samples of the selected soils were prepared with the same soil dry density. For preparing treated samples, in place of water, NRL was added to soil. The results of one-dimensional swelling-compression tests demonstrated that in low and medium plastic soils, NRL treatment increased the swelling potential marginally, whereas it considerably reduced the swelling in the high plastic soil, which is expansive in nature. NRL did not cause any changes in the swelling pressure of medium plastic soil. At the same time, it brought about a considerable drop in the swelling pressure of high plastic soil. In the consolidation tests, a decrease in compressibility, quantified in terms of compression index, was observed in all soils after NRL treatment. The resilient nature of rubber content caused an increase in the recompression index in all treated samples. A reduction in the coefficient of consolidation was observed in NRL-treated soils. The study concludes that despite the high deformability of rubber, NRL treatment does not negatively affect the swell-compression behaviour of soils. Besides, the treatment effectively controls the swelling and compression of highly compressible soil.

Construction resting on soil and rocks containing montmorillonite (MMT) are prone to damage induced by swelling, which involves a significant release of energy. It is often desirable to enhance these soils to mitigate swelling potential, regulate volume changes, and manage energy release. Experimental findings suggest that increasing temperature is one method to improve these soils, with water content, initial volume, and boundary conditions also influencing the swelling mechanism. This study utilizes ab initio molecular dynamics calculations to explore changes in volume and energy within MMT unit cells at the nanoscale due to temperature variations. The response of unit cells of MMT with varying dimensions and quantities of water molecules to temperature is assessed under constrained and unconstrained conditions. Results indicate that the volume changes and energy release of unit cells in response to temperature are contingent upon the presence of water molecules. In unit cells containing water molecules, both energy and volume decrease with rising temperature, whereas in unit cells devoid of water molecules, energy decreases while volume increases as temperature rises. Given the inherent association of soils with water in natural settings, it can be deduced that increasing temperature presents a viable method for enhancing naturally occurring MMT-dominated soils. Density functional theory calculations demonstrate that alterations in the volume and energy of MMT stem from shifts in interactions among the minerals, cations, and water molecules, as well as intrinsic structural defects like isomorphic substitution and peroxy links within the unit cells. These modifications induce variations in charge carriers and electrical properties, consequently influencing volume and energy changes within MMT unit cells. Additionally, it was observed that the failure of peroxy links can significantly impact the optimal temperature selection for the thermal enhancement of MMT.