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Highly plastic clays pose significant challenges in engineering projects. Various techniques have been employed to enhance their properties, though many face difficulties related to implementation and environmental impact. This study examines the effect of CO2-induced magnesium carbonate on improving the geotechnical behavior of plastic clay. CO2-induced magnesium carbonate was produced via mineral carbonation and used to improve the behavior of highly plastic natural clay. CO2 gas was injected into a sodium hydroxide solution to produce carbonate ions (CO32−). Magnesium carbonate was precipitated on a laboratory scale by adding magnesium sulfate solution to the carbonate ion solution. Clayey soil samples were obtained from test pits in the Meyghan Plain near Arak, Iran. The clay samples were treated with different percentages of the produced magnesium carbonate. Various parameters of the treated and untreated samples, including index properties, unconfined compressive strength, consolidation behavior, and swelling potential, were studied. It was found that the liquid limit and plasticity index of the treated clay decreased as the magnesium carbonate content increased. The soil classification changed from high plastic clay (CH) to low plastic silt (ML) with the addition of 15% magnesium carbonate to the highly plastic clay. The unconfined compressive strength of the treated clay increased. Additionally, the consolidation behavior and swelling index of the treated clay improved as the magnesium carbonate content increased. This study confirms that CO2-induced magnesium carbonate is a promising material for improving the behavior of highly plastic clays, offering a sustainable approach to environmental management. [ABSTRACT FROM AUTHOR]

The article focuses on the monitoring and disaster prevention strategies for high and steep sandstone slopes along highways under construction, emphasizing a case study in Guangxi, China. It also discusses the implementation of intelligent monitoring systems, the analysis of early warning data, and the application of emergency rescue measures to prevent slope collapses, including the use of counterpressure and anchor piles.

This research study was conducted to improve the properties of highly plastic clay using carbonate minerals produced using carbon dioxide. The carbonates such as magnesite, siderate and calcite were produced using laboratory-scale carbonation experiments and were used to treat clay samples. The index properties, shear strength and consolidation behaviour of the treated clay samples were then investigated. The results showed that the plasticity index and activity of the treated clay decreased, and shear strength and consolidation behaviour improved. The study confirmed that magnesite had improved clay properties due to the uniform and homogeneous distribution of small crystals of magnesite in the clay compared with those of siderite- and calcite-treated soil. As the process sequesters carbon dioxide, it could be developed as an environmentally friendly soil improvement method subject to further research studies. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the structure and shape of carbonate crystals induced through microbial activity and carbon dioxide reactions in the sand. The strength of sandy soil treated with carbonate minerals was subsequently determined using unconfined compression strength (UCS) tests. Sporoscarcina pasteurii bacteria were used to produce an aqueous solution of free carbonate ions (CO32−) under laboratory circumstances called microbial-induced carbonate precipitation (MICP). In CO2-induced carbonate precipitation (CICP), carbon dioxide was added to a sodium hydroxide solution to form free carbonate ions (CO32−). Different carbonate mineral compositions were then provided by adding Fe2+, Mg2+, and Ca2+ ions to carbonate ions (CO32−). In the MICP and CICP procedures, the results of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) revealed a distinct morphology of any type of carbonate minerals. Vaterite (CaCO3), siderite (FeCO3), nesquehonite (MgCO3(H2O)3), and dolomite (CaMg(CO3)2 were produced in MICP. Calcite (CaCO3), siderite (FeCO3), nesquehonite (MgCO3(H2O)3), and high-Mg calcite (Ca-Mg(CO3)) were produced in CICP. According to UCS data, siderite and high-Mg calcite/dolomite had more effectiveness in increasing soil strength (63–72 kPa). The soils treated with nesquehonite had the lowest strength value (25–29 kPa). Mineral-treated soils in CICP showed a slightly higher UCS strength than MICP, which could be attributable to greater particle size and interlocking. This research focused on studying the mineralogical properties of precipitated carbonate minerals by CICP and MICP methods to suggest a promising environmental method for soil reinforcement. [ABSTRACT FROM AUTHOR]

There are standard techniques to remove and stabilize petroleum-contaminated soils to prevent or minimize the release of contaminants into the environment. Carbon dioxide (CO2), an air pollutant, is an important heat-trapping (greenhouse) gas that causes global warming. In this paper, utilization of CO2-induced magnesite minerals in remediation and stabilization of diesel-contaminated sandy soil were evaluated in laboratory-scale experiments. Indeed, this study has two environmental advantages, one reduction of CO2 emission and petroleum removal from soil environment. Soil specimens containing contamination of about 5% and 10% of diesel contents were prepared. The magnesium carbonate hydrate (Nesquehonite) was produced by a CO2-induced process and added to contaminated samples in 10, 15, and 20% plus 2.5% Portland cement. The UCS, permeability, TPH, and SEM tests were conducted on the pieces. The Portland cement increased the compressive strength of contaminated samples while it was found a reduction of total petroleum hydrocarbons (TPH) by about 29%. Maximum diesel removal efficiency was obtained at treated samples with 20% magnesium carbonate and 2.5% cement, about 90% reduction. SEM images of treated soil samples indicated that the higher absorption capacity of magnesium carbonate was related to needle/blade shape particles.Article Highlights: Utilize of CO2 to precipitate of magnesium carbonate hydrate (Nesquehonite) Remediation of diesel-contaminated sandy soil by magnesium carbonate Stabilization of diesel-contaminated soil by CO2-induced magnesite precipitation [ABSTRACT FROM AUTHOR]