Dispersive soils, due to their high erodibility and cation exchange sensitivity, pose significant challenges in geotechnical applications. This study investigates the engineering behavior of such soils under a wide range of thermal regimes (25-900 degrees C), focusing on their mechanical, hydraulic, and physicochemical properties. Unlike previous studies that emphasized microstructure alone, this research integrates a broad range of analytical methodsmineralogical (XRD, SEM), chemical (CEC, SSA, carbonate content), and geotechnical (Atterberg limits, unconfined compressive strength, permeability, TGA) to capture a comprehensive understanding of thermal stabilization effects. Results reveal that thermal treatment significantly enhances soil performance: at 300 degrees C, dispersion decreased by 65% due to complete free water removal; at 500 degrees C, dehydroxylation induced structural rearrangement and mineral breakdown, improving both strength and permeability. At 700 degrees C and beyond, the formation of cementitious phases such as gehlenite and anorthite transforms the soil into a dense, non-dispersive medium, increasing UCS by 36.5 times and permeability by 12,000 times. These findings emphasize the effectiveness of high-temperature treatment as a sustainable and technically sound approach for stabilizing dispersive soils in geotechnical and environmental applications, including landfill liners, geothermal barriers, and contaminant containment zones.

The studied region is located in the southwestern Iran and on the border of Iran and Iraq. In the past, this region had dense palm groves and abundant plants. However, due to the decrease in upstream discharge, in recent years, saline and sodium seawater has intrusion in the river and affected the agricultural lands along its sides. This event has caused irreparable and serious damage to the agricultural industry in the region, turning this area into a graveyard of date palm trees. Understanding the characteristics of agricultural soils for their improvement and/or planting appropriate plants is one of the goals of sustainable agriculture. Considering the damage of the studied area from the intrusion of salt water in the Arvand River, this study investigated important characteristics of soil salinity including EC, pH, C.E.C, SAR and ESP. In this research, sampling of agricultural soils along the riverside was carried out in three different horizons and two line parallel to the river and at two different distances. Statistical methods of correlation coefficient, hierarchical analysis and factor analysis were used to identify the factors affecting soil quality and the relationships between parameters. The results showed that due to the intrusion of sodium seawater, the soils of the studied area have become saline-sodium, and the salinity level in the soils near the river mouth is higher than that in the soils on the upstream side of the river. In terms of fertility, the cation exchange capacity is in the medium range, and the clay texture and abundant organic matter of the soil as a result of the remaining plant and tree residues have an important effect on this parameter.

In this paper, the experimental findings on the use of Limestone Calcined Clay Cement (LC3) in the stabilization of sub-grade expansive soils are reported. The effect of LC3 on mechanical properties of subgrade soil was investigated experimentally through the soaked California Bearing Ratio (CBR), Proctor and Atterberg limits tests. The difference in the performance between LC3 and Ordinary Portland Cement (OPC) treated subgrade soils was studied for comparison purposes. The LC3 and OPC stabilizers were separately mixed with the soil in the proportions of 1%, 1.5% and 2% by dry weight of the soil. The results showed that the addition of both LC3 and OPC increased plastic limit, reduced plastic index, liquid limit and linear shrinkage of the treated soils. The Maximum Dry Density (MDD) of the soil was observed to increase with a corresponding decrease in Optimum Moisture Content (OMC) upon adding varying cement dosages. Additionally, the soaked CBR of the treated soil was observed to increase significantly with increasing cement content. The maximum CBR and MDD improvement were observed at 2% cement dosage, while OMC was reduced, hence, it could be regarded as the optimum dosage for soil stabilization. The performance between LC3 and OPC treated subgrade was quite comparable. In conclusion, LC3 was found to improve the strength and stability of subgrade soil.

As a typical special soil, red clay found in Guizhou Province, China, must be improved before it can be used for projects owing to its high plasticity. As a soil curing agent, the Consolid system is applicable to a wide range of soils, has good improvement effects and a simple operation, and is environmentally friendly. The effects of the dosage and curing age of the Consolid system on the unconfined compressive strength and shrinkage properties of the cured red clay-gravel mixture are studied. The results showed that both these properties of the red clay-gravel mixture were significantly improved by the Consolid System, and the higher the dosage of the Consolid system, the better the improvement effect. The thermal methods of thermogravimetric analysis and differential scanning calorimetry were used to determine that the bound water content was related to the amount of Consolid system admixture. With the increase in the dosage of the Consolid system, the weakly bound water content of red clay appeared to be reduced to different degrees, while the strongly bound water content was reduced to a lesser extent. The reduction in the weakly bound water led to an increase in the molecular gravitational force between the soil particles. This promoted the agglomeration of the soil particles to form a stronger agglomerate structure, thereby enhancing its mechanical properties. The physical phase analysis of cured soils with different amounts of Consolid system admixture was carried out by X-ray diffraction analysis. No chemical reaction occurred during improvement, but the crystal spacing was reduced. This phenomenon could be a factor improving the shrinkage properties. In addition, the shrinkage properties of the soil improved because of the low number of exchangeable cations on the mineral surface, allowing the cured soil to enter a charge equilibrium state quickly.

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.

Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+ tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multidentate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research.