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.

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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.

The structure and shape of carbonate crystals formed by microbial activity and carbon dioxide reaction were investigated in this work. The mineral carbonates treated sandy soil was subsequently determined using unconfined compression tests (UCS). 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, carbon dioxide was added to a sodium hydroxide solution to form free carbonate ions (CO32-) (CICP). 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 carbonate minerals. Vaterite (CaCO3), siderite (FeCO3), magnesium carbonate hydrate, or Nesquehonite (MgCO3 (H2O) 3) and dolomite (CaMg(CO3)2) were produced in MICP. Calcite (CaCO3), siderite (FeCO3), magnesium carbonate hydrate or Nesquehonite (MgCO3 (H2O) 3), and high-Mg calcite (CaMg(CO3)2) were produced in CICP. The results of UCS showed that siderite and high-Mg calcite /dolomite had more efficiency in soil strength. The lowest value of strength was related to magnesium carbonate hydrate treated soils. Mineral-treated soils in CICP showed a slightly higher UCS strength than MICP, which could be attributable to greater crystal particle sizes and particle interlocking.