The use of nano-materials as a stabilizing agent in soils has a significant role, particularly in improving their mechanical properties. This study investigates the impact of stabilization using nano-materials, specifically nano-cement, on natural and contaminated clays. A series of laboratory tests, including Atterberg limits, compaction, unconfined compressive strength, permeability, and consolidation, are conducted to evaluate the soil properties. Various percentages of nano-cement (0 %, 0.5 %, 1 %, 1.5 %, and 2 %) are added to two sample groups; one prepared with water and the other with leachate. Based on the results of Atterberg limits tests, adding 2 % nano-cement to natural clay increases the liquid limit by 8.6 % and decreases the plasticity index by 16 %. These values diminish to 8.3 % and 13 % for contaminated clay. Furthermore, according to the compaction test results, increasing nano-cement content by up to 2 % leads to a reduction in maximum dry density by about 11.5 % and an increase in optimum moisture content by about 15.9 %. However, these values change to 5.77 % and 32.25 % for contaminated clay. The results indicate that increasing nano-cement content generally improves the strength and stiffness of the soil while reducing its permeability. On the other hand, contamination of the soil leads to a reduction in strength and stiffness, while permeability increases. Based on the Field Emission Scanning Electron Microscopy (FESEM) analysis, the incorporation of nano-cement improved the microstructure by decreasing pore spaces and enhancing bonding between particles. While chemical complexity of leachate negatively affects nano-cement dispersion, which leads to increased particle aggregation.

The environmental impact of red mud leachate, particularly from tailings ponds, has become a significant concern due to its highly alkaline nature and potential to cause widespread soil and water contamination. Addressing this issue requires effective strategies for mitigating the leakage of contaminants, such as heavy metals and hazardous alkalis, into surrounding ecosystems. This study explores the use of fly ash-modified clay liners as a solution to contain and treat red mud leachate pollutants, including heavy metals and alkalis. Macro-scale tests, such as permeation and unconfined compression tests, combined with micro-scale analyses (XRD, SEM, BET), investigate the influence of varying fly ash content on the hydraulic conductivity, mechanical properties, and microstructure of the clay liners. The findings show that fly ash significantly reduces the hydraulic conductivity of the liners, improving their effectiveness in preventing seepage. It also enhances the liners' ability to adsorb heavy metal ions and increases their mechanical strength, especially cohesion, with optimal performance at a 9 % fly ash content. The study further reveals that pozzolanic reactions in the alkaline environment of red mud lead to the formation of cementitious gel binders (C-S-H, C-A-H), which reduce pore sizes and create a denser, more impermeable structure. These improvements in both physical and chemical stability demonstrate the potential of fly ash-modified clay liners as an effective, sustainable solution for managing red mud tailings ponds. This study provides valuable support for environmental management of red mud tailings ponds and the sequestration of red mud leachate waste.

This study investigates the physicochemical properties of Soil-Like Material (SLM) recovered from aged Municipal Solid Waste (MSW) dumps in Anantapur, Andhra Pradesh, India, and assesses its potential for reuse. The SLM, which constitutes 68%-75% of the excavated waste, was analyzed for key parameters including total dissolved solids (TDS), chemical oxygen demand (COD), electrical conductivity (EC), and heavy metal concentrations. Results revealed that the organic content of SLM ranged from 6% to 20%, significantly higher than that of local soils (1.5%). The leachate produced from SLM showed elevated levels of TDS (500-1,200 mg l-1), COD (150-270 mg l-1), and heavy metals such as copper (Cu), lead (Pb), chromium (Cr), and zinc (Zn). Cu and Pb concentrations were found to be 27 and 26 times higher than those in local soil extracts, posing substantial risks to groundwater and soil quality. Other metals, including nickel (Ni), arsenic (As), and cadmium (Cd), also exceeded permissible limits. These findings suggest that while SLM has potential for reuse, its high contamination levels require treatment methods such as soil washing, heating, or stabilization with additives like lime or fly ash to reduce environmental risks. Without proper treatment, the direct use of SLM could result in substantial ecological damage. The study highlights the importance of sustainable landfill site rehabilitation and the development of safe strategies for the reuse of SLM to mitigate potential environmental impacts.

In this study, laboratory aging experiments are conducted to examine the aging effect on the interface shear behavior between soil and geomembrane. In the first stage, the geotechnical index and shear strength parameters of the soils are determined through laboratory experiments. The second stage focuses on examining the shear strength behavior of soil-geomembrane interfaces. The study examines commonly used geomembranes in the world, such as high-density polyethylene and thermoplastic polyolefin. Different synthetic waste leachates prepared in laboratory conditions are used to simulate real field conditions. The aging effects of geomembranes are examined by subjecting them to different pore liquids in the curing pool for 16 months. The surface deformations and roughness of the geomembranes used in the experiments are analyzed using scanning electron microscopy and optical profilometer. The study evaluates the effects of soil properties, pore liquids, and aging on the geomembrane surfaces. Soils with more coarser grains exhibited higher interface friction angles. It has been determined that the interface friction angles were significantly adversely affected by all curing liquids. Acidic mine drainage was found to have the most detrimental effect on the interface friction angles of geomembranes, while coal combustion product leachate caused minimal damage. The results from optical profilometer and scanning electron microscopy analysis aligned with the interface direct shear test results, further supporting the findings from the experiments. The study has shown that the design interface friction resistances are not sufficient for geomembranes exposed to chemicals in the long term. This aspect should be taken into consideration when creating design parameters.

This study investigates the potential application of a blend, termed GGRM, consisting of red mud (RM) and ground-granulated blast furnace slag (GGBS), for stabilizing subgrade expansive soil. RM, an industrial waste from aluminium refineries, poses environmental concerns due to its high alkalinity and presence of heavy metals. Despite its increased utilization in construction sector, research on its role in soil stabilization is limited. With this in mind, RM has been used as an activator for GGBS, to create synergy between these industrial wastes with an objective to utilize this blend for stabilization of black cotton soil (BCS). Therefore, laboratory investigations were conducted to assess the strength of BCS stabilized with GGRM comprising varying proportions of GGBS and RM (0:100, 70:30, 50:50, 30:70, and 100:0 by weight). Further, the optimal GGRM quantities were evaluated by mixing it in different proportions (5-30% by weight). This study also examined the effect of curing on strength properties and leaching behaviour and investigated the associated mechanisms through microstructural studies (XRD, XRF, SEM, and FTIR analysis). The leachate potential was assessed using ICP-OES analysis. Results indicated a maximum sevenfold improvement in unconfined compressive strength of BCS, from 131 to 920 kPa, after 28 days of curing in 70:30 combinations with 25% GGRM content. Furthermore, leaching of heavy metals from stabilized soils are within the permissible limits of hazardous waste management regulations. In conclusion, RM-activated GGBS blends emerged as a potentially sustainable binder, enhancing the strength of expansive soil for subgrade applications.

Lysimeters are frequently employed to replicate environmental conditions in landfill scenarios due to their relatively economical nature and brief study duration. Lysimeters frequently exhibit varying geometrical characteristics that modify the physical and thermodynamic attributes, potentially influencing waste material's decomposition rate and leaching dynamics. Based on the results of the lysimeter tests, lysimeters effectively evaluate and predict the impact of magnesium oxide (Mgo), a material suitable for constructing landfill liners. The findings substantiate that lysimeter investigations can significantly contribute to landfill engineering by identifying optimal strategies for waste containment and selecting appropriate materials for fabricating landfill barriers. Throughout the experimental procedure, the lysimeter was subjected to leachate application. In each hour of the experiment, the quantities of moisture, electric conductivity value (EC), temperature, settlement, pressure reaching the liner, and the total volume and pH of the obtained effluents were measured each week. This research explores and analyzes the role of magnesium oxide (C-M) in reducing permeability and measuring the shear strength properties of the composite material by utilizing a triaxial test. The sensor results demonstrated that MgO-enhanced liners provided superior long-term performance compared to clay. EC sensors showed MgO liners had lower and more stable conductivity. Moisture content sensors indicated that MgO-treated soil maintained better moisture regulation, reducing leachate. LVDT sensors revealed that MgO liners had minimal settlement, while clay experienced greater and prolonged settlement. Temperature sensors confirmed MgO's consistent thermal stability. In contrast, pressure, Total Dissolved Solid (TDS), pH, and flow rate sensors highlighted MgO's better structural integrity, lower dissolved solids, and controlled permeability over time.

Red mud, a by-product generated during the extraction of aluminium from bauxite ore, poses challenges to the alumina industry due to its inherent sodicity, alkalinity and heavy metal content. Consequently, studies related to its bulk utilization and valorization have gained attention in the construction sector to promote sustainability. However, utilization of red mud in stabilization of expansive soils using alkali activation is seldom explored. Therefore, this study focuses on improving the geotechnical properties of an expansive soil (black cotton soil, BCS) through chemical stabilization by using blends of two distinct industrial wastes, viz. red mud and GGBS, termed as GGRM, activated with sodium hydroxide (NaOH) solution. The strength, stiffness and durability characteristics of these compacted blends were assessed based on a series of laboratory investigations like unconfined compressive strength, ultrasonic pulse velocity and wet-dry cycles tests. Leachate analysis was also performed to assess the geo-environmental issues of soil ameliorated with blends of alkali-activated GGRM blends. These blended specimens were moulded with different molar concentrations of NaOH solutions (i.e. 2, 5 and 10 M). Further, microstructural studies were carried out through XRD, SEM-EDS and FTIR analysis. The results show that heavy metal contents in alkali-activated specimens are within the permissible limits of USEPA guidelines. Based upon the assessments of strength, durability and P-wave velocity after 28 days of curing period, 25 and 30% binder contents of GGRM100:00, GGRM70:30 and GGRM50:50 corresponding to 5 M and 10 NaOH, were found suitable for subgrade applications in accordance with IRC 37 guidelines.

This study investigates the long-term effects of landfill leachate contamination on soil hydraulic conductivity and shear strength parameters over a 12-month period, addressing the current lack of comprehensive long-term experimental data in this field. Laboratory permeability tests and direct shear tests were performed on sandy clayey silt samples contaminated with leachate at concentrations ranging from 5% to 25%. Microstructural and mineralogical analyses were conducted using SEM and XRD to identify the mechanisms behind observed changes. The results identify a critical threshold at 15% contamination where soil behavior transitions from granular to cohesive characteristics, marked by significant changes in both hydraulic and mechanical properties. Hydraulic conductivity increases at low contamination levels but decreases significantly at higher levels, while friction angle shows an immediate reduction from 36.5 degrees to 31-31.5 degrees and cohesion exhibits a three-phase evolution pattern, reaching peak increases of 151.5% at 15% contamination. The hydraulic conductivity changes are controlled by contamination level rather than exposure time, maintaining stable values throughout the testing period, whereas shear strength parameters demonstrate more complex temporal evolution patterns. These findings provide essential parameters for landfill design and stability assessment, demonstrating how leachate concentration affects long-term soil behavior through mineral formation and structural modification.

The storage of mining waste not only consumes a vast tract of land, but it also poses environmental problems due to the leaching of heavy metals, dusting, and occasional slope failure. A coal mine overburden (hereafter referred to as black shale) is one of the mining wastes produced during the coal mining activity, dumping of which causes an environmental problem. By considering the issue associated with waste storage and the requirement for alternate civil engineering material, an attempt has been made to develop cementless controlled low strength material (CLSM) from black shale. For this purpose, black shale is mixed with a varying percentage of alkali activated ground granulated blast furnace slag (GGBS) and fly ash. The fresh CLSM is investigated for flowability, bleeding, and density, whereas the hardened CLSM is examined for unconfined compressive strength (UCS), hardened density, water absorption, ultrasonic pulse velocity, and durability. The CLSM developed in the present research is found to have self-flowing and self-leveling consistency, with flowability higher than 200 mm and a relative flow area between 2.06 and 7.70. The CLSM is found easily excavatable with a removability modulus less than 1. The 28-day UCS of CLSM is found between 0.48 MPa and 2.1 MPa, whereas it is found low to medium durable with a durability index between 84.44 % and 87.39 %. Further, the shear modulus of the hardened CLSM is evaluated using ultrasonic pule velocity. Finally, the CLSM is found non-toxic based on the result of the leaching analysis.

Inadequate management of solid waste stands out as a primary cause of environmental contamination, leading to a decline in groundwater quality in the vicinity of landfill sites. Though landfills are required by federal regulation to have liners formed by plastic or clayey layers, these liners tend to have leaks, which can result in landfill leachate percolation into the soil and aquifers, contaminating nearby water sources and further damaging ecosystems. Currently, the elevated nitrate (NO3-) concentration in groundwater spurred by landfill leachates is becoming a growing global concern. Various regions across the world present groundwater NO3- concentrations exceeding the threshold limit (50 mg/L) of WHO for drinking purpose. In this scenario, it is requisite to consider and develop highly efficient and affordable solutions for the long-term management of groundwater resources. Therefore, a bibliographical review was conducted in this paper by searching literature in Web of Science, ScienceDirect, Google Scholar, SpringerLink, PubMed, and Scopus to analyze NO3- pollution in groundwater caused by landfill leachates and explore the impacts of landfills and NO3- pollution on the environment and human health. In addition, this review also presents an overview of the leachate treatment technologies to remove nitrogenous compounds, particularly NO3-. This review entails a worldwide appraisal of groundwater NO3- pollution to comprehend the human health risks and aid in optimizing groundwater quality. A resulting framework developed in this review provides an improved grasp of the link between inadequate landfill management and adverse environmental and health outcomes and urged all stakeholders to address the issue of solid waste to ensure environmental and human health. Overall, the results emphasize the need for immediate action and collaborative efforts to mitigate these impacts and ensure the long-term sustainability of waste management practices.