This study investigated the impact of optimum dosages of nano-calcium carbonate (nano-CaCO3) and nanosilica on the engineering behavior of black cotton soil. The desired percentage of nano-addition, 2%, for both nanomaterials, was determined by analyzing the plasticity-compaction characteristics and the relative strength index values of treated samples. The study unveiled that the entire clay microstructure was transformed into a nanocrystalline matrix after treatment. The deviatoric strength enhancement with confining pressure and curing period was significant after treating the soil with either nano-CaCO3 or nanosilica. The nanosilica treatment was found to be more effective in improving the California bearing ratio (CBR) strength of black cotton soil samples compared with nano-CaCO3 stabilization. The addition of nanomaterials induced the formation of nanocrystalline hydrate gels and silica gel, resulting in an increased resistance to volumetric deformation under compressive stresses. The hydraulic conductivity of nano-treated samples dropped due to the highly tortuous networks between pores in the nano-crystalline structure. The experimental results were substantiated by analyzing the microstructure of nano-treated soils using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) techniques.

Civil engineering structures made upon expansive soils known in India as Black Cotton (BC) soils are susceptible to structural damages due to their seasonal swell-and-shrink behaviour. This study focuses on assessing the mechanical performance of BC soil stabilised using unconventional binders, specifically Sugarcane Bagasse Ash (SCBA) and Ground Granulated Blast Furnace Slag (GGBS) with different proportions. The experimental evaluation included Compaction tests, Unconfined Compressive Strength (UCS) tests, Triaxial tests, and Atterberg's limits tests. Additionally, mineralogical and morphological studies were carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and chemical analysis using x-ray fluorescence spectroscopy analysis (XRF). The results showed that the mixture containing 21% SCBA and 9% GGBS produced cementitious-siliceous-hydrate (C-S-H) molecule, which improved the strength. Based on the soil-binder percentage ratio obtained from UCS tests, a regression equation was developed to estimate consolidated soil strength. The regression model, exhibiting an impressive R2 value of 93.69%, was analysed within the framework of existing empirical correlations by other researchers. This statistical model, with its good fit, is a useful tool for evaluating the compressive strength of stabilised expansive soil. The findings provide insights into successful stabilisation solutions for expansive soils found locally and globally.

Black cotton (BC) soil poses threats to build structures owing seasonal volumetric changes. The production of fly ash (FA) and bagasse ash (BA) increasing abundantly, and their improper disposal poses detrimental effects on the environment and human health. This research aims to develop sustainable, novel, optimum binary blend by using FA and BA to improve the strength characteristics of the BC soil after curing periods of 7, 14, and 28 days. BA was mixed in different ratios by dry weight of FA to obtain the optimum binder based on maximum UCS. The optimum binder comprising of 80:20, mix by dry weight of BC soil in varying proportions. The effects of mix show significant changes in the geotechnical and mechanical properties of BC soil. Research shows that swelling features reduces alters into non-swelling soil. The soil transitions from a plastic to a brittle state. The results revealed that MDD, UCS, CBR and STS increases significantly with curing periods. The mineralogical and microstructural test carried out using XRD and SEM, which supports the creation of cementitious complex and development of a dense matrix. The results state that utilized binder to stabilize BC soil is suitable for civil infrastructure specially pavement and foundations.

In this study, the potential use of industrial waste materials, namely, copper slag (CS), iron ore tailings (IOT), and red mud (RM), as stabilizing agents for black cotton (BC) soil in pavement construction applications was evaluated. Laboratory tests were conducted to assess the performance of the stabilized BC soil, including Atterberg limits, compaction characteristics, California bearing ratio (CBR), unconfined compressive strength (UCS), permeability, and fatigue tests. Additionally, microstructural analysis was performed to further investigate the changes in the soil properties. The results indicated that BC soil mixed with CS, IOT, and RM exhibited enhanced plasticity, strength (UCS and CBR), permeability, and fatigue properties compared to untreated BC soil, regardless of the mix percentage. Notably, BC soil with 30% CS demonstrated comparable results to BC soil stabilized with 5% cement, significantly improving its properties. This study addressed a gap in pavement engineering research by evaluating the fatigue behavior of stabilized subgrade soils. It was concluded that incorporating 30% CS into BC soil not only enhanced its performance but also provided a sustainable alternative to traditional stabilizers such as cement and lime.

Expansive soils pose various problems to the existing transportation infrastructures by causing damages to pavements, railways, and embankments due to differential settlement, and volume changes in soils. Therefore, expansive soil if used in pavements must be stabilized by using some suitable means. The present study investigates the strength and durability of expansive soil stabilized with alkali-activated GGBFS (ground granulated blast furnace slag). In order to accelerate the hydration process, an alkali activator of low molarity (i.e., 5 M NaOH) is used to stabilize the subgrade expansive soil. GGBFS and alkali-activated GGBFS were added in the proportions of 5, 10, 15, 20, 25, and 30% to check the improvement in the strength properties of expansive soils after different periods of curing. The strength properties of stabilized soil were assessed by conducting various laboratory tests like unconfined compressive strength (UCS) and California bearing ratio (CBR). Durability study was also done by subjecting the soil specimens to 12 wet-dry cycles. The utilization potential of alkali activated GGBFS has been assessed from the mechanical, mineralogical, and morphological properties of stabilized soil. It was found that alkali-activated GGBFS can be effectively utilized for highway subgrade and sub-base applications.

The present study investigated the evolution of the time-dependent behavior of remolded samples of Indian black cotton soil for different loading-unloading-reloading cycles in oedometer conditions. The microstructural analysis was carried out to evaluate the parameters such as particle rearrangement and pore size reduction that are responsible for creep at different time periods. It was observed that micropores existed in large numbers, and the number of pores decreased rapidly with an increase in pore size. The number of pores was found to decrease by 20-30% and 85-90% at the intermediate and final stages of the creep test, respectively. Additionally, it was noted that although small pores and mesopores were less in number, they were significant in pore area calculations. The reduction in pore areas for the intermediate and final stages was found to be in the range of 40-50% and 40-60%, respectively, as there were large proportions of micropores that compressed without influencing the overall pore area. The percentage of vertically aligned particles reduced from 21 to 15% at the end of the test. This observation is attributed to the particle rearrangement and reduction in pore sizes that occurred during the test.

The East Asia black cotton soil (BCS) cannot be used as embankment filling directly due to its high clay content, liquid limit, plasticity index, and low CBR strength (CBR < 3%). This study evaluates the effects of treating East Asia BCS with lime, volcanic ash, or a combination of both on its engineering properties. Experiments were conducted to analyze the basic physical properties, swelling characteristics, and mechanical properties of the treated soil. Results indicate that lime addition significantly reduces the free swelling rate, improves limit moisture content, increases optimum moisture content, decreases maximum dry density, and enhances CBR value. Although volcanic ash also improves BCS performance, its effects are less pronounced than those of lime. The combined treatment with lime and volcanic ash exhibits superior performance, greatly reducing expansion potential and significantly increasing soil strength. Specifically, a mixture of 3% lime and 15% volcanic ash optimizes the liquid limit, plasticity index, and CBR value to 49.2%, 23.8, and 24.7%, respectively, meeting the JTG D30-2015 requirements and reducing construction costs. The treatment mechanisms involve hydration exothermic reactions, volcanic ash reactions, and semipermeable membrane effects, which collectively enhance the soil's properties by producing dense, high-strength compounds.

This paper discusses efforts made by past researchers to steady the expansive (problematic) soils using mechanical and chemical techniques - specifically with EPS beads, lime and fly ash. Administering swelling of problematic soils is critical for civil engineers to prevent structural distress. This paper summarizes studies on reduction of swelling potential using EPS, lime and fly ash individually. Chemical stabilization with lime and fly ash are conventional methods for expansive soil stabilization, with known merits and demerits. This paper explores the suitability of different materials under various conditions and stabilization mechanisms, including cation exchange, flocculation, and pozzolanic reactions. The degree of stabilization is influenced by various factors such as the type and amount of additives, soil mineralogy, curing temperature, moisture content during molding, and the presence of nano-silica, organic matter, and sulfates. Additionally, expanded polystyrene (EPS) improves structural integrity by compressing when surrounded clay swells, reducing overall swelling. Thus, EPS addresses limitations of chemicals by mechanical means. Combining EPS, lime and fly ash creates a customized system promoting efficient, long-lasting, cost-effective and eco-friendly soil stabilization. Chemicals address EPS limitations like poor stabilization. This paper benefits civil engineers seeking to control expansive soil swelling and prevent structural distress. It indicates potential of an EPS-lime-fly ash system and concludes by identifying research gaps for further work on such combinatorial stabilizer systems.

Geosynthetic clay liners (GCLs) are mostly used as flow barriers in landfills and waste containments due to their low hydraulic conductivity to prevent the leachate from reaching the environment. The self-healing and swell-shrink properties of soft clays (expansive soils) such as bentonite enable them as promising materials for the GCL core layers. However, it is important to modify their physico-chemical properties in order to overcome the functional limitations of GCL under different hydraulic conditions. In the present study, locally available black cotton soil (BCS) is introduced in the presence of an anionic polymer named carboxymethyl cellulose (CMC) as an alternative to bentonite to enhance the hydraulic properties of GCL under different compositions. The modified GCL is prepared by stitching the liner with an optimum percentage of CMC along with various percentages of BCS mixed with bentonite. Hydraulic conductivity tests were performed on the modified GCL using the flexi-wall permeameter. The results suggest that the lowest hydraulic conductivity of 4.58 x 10-(10) m/s is obtained when 25% of BCS is blended with bentonite and an optimum 8% CMC and further addition of BCS results in the reduction of the hydraulic conductivity.

To enhance the mechanical properties of problematic black cotton soil, engineers are focusing on reinforcing the soil with geosynthetic materials. This attention is particularly directed towards improving the strength characteristics of black cotton soil, given its inherent challenges associated with volume changes and plasticity. In this comprehensive study, red stone dust waste is introduced in varying percentages ranging from 5% to 35% to stabilize the black cotton soil. The goal is to assess the impact of different proportions of red stone dust on the stabilization of the soil. Furthermore, to augment the stability of the soil, polymer fabric is strategically incorporated at different depths, both in single and double layers. The California Bearing Ratio (CBR) tests are conducted on blends of black cotton soil and red stone dust, with the polymer fabric positioned at depths of H/3 and 2H/3 from the top of the loading surface. The results indicate that the blend containing 25% red stone dust yields the most favorable outcomes in terms of CBR improvement. Additionally, it is observed that the enhancement in CBR values is more pronounced when the reinforcement is applied in a single layer compared to double layers. In summary, the study reveals that the combination of red stone dust and polymer fabric reinforcement offers a promising approach for effectively stabilizing black cotton soil, with the optimal percentage of red stone dust and the configuration of the reinforcement layers playing crucial roles in CBR values.