Thermodynamic Evaluation of Smectite Treated with Hydrogen Ion Stabilizer

Akula, Pavan; Little, Dallas N.; Schwab, A. P.

doi:10.1061/(asce)mt.1943-5533.0003186

Cited by 6 publications

(3 citation statements)

References 25 publications

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“…In the case of the unaltered basalt powder, no noticeable changes were made to the mineral composition after dissolution. Conversely, for altered basalt, a marked decrease in the intensity of the smectite peak at 5.9° was observed, 40 suggesting a selective dissolution of smectite. Additionally, the overlapping peak belonging to plagioclase and pyroxenes at 27.8° decreased significantly, whereas the peaks for plagioclase alone, such as at 22.0°, decreased to a lesser extent, suggesting a preferred dissolution of pyroxene over plagioclase.…”

Section: Resultsmentioning

confidence: 97%

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization

Wang,

Yagi,

Tamagawa

et al. 2024

ACS Omega

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Hydrothermally altered basaltic rocks are widely distributed and more accessible than fresh basaltic rocks, making them attractive feedstocks for permanent CO 2 storage through mineralization. This study investigates the reactivity and dissolution behaviors of altered basalt during the reaction with CO 2 -rich fluids and compares it with unaltered basalt through batch hydrothermal experiments using a brine that simulates reservoir conditions with 5 MPa CO 2 gas at 100 °C. When using basalt powders to evaluate reactivity, results show that although the leaching rates of elements (Mg, Al, Si, K, and Fe) from altered basalt were generally an order of magnitude lower than those from unaltered basalt in a CO 2 -saturated acidic environment, similar elemental leaching behavior was observed for the two basalt samples, with Ca and Mg having the highest leaching rates. However, in a more realistic environment simulated by block experiments, different leaching behaviors were observed. When the CO 2 -rich fluid reacts with altered basalt, rapid and preferential dissolution of smectite occurs, providing a significant amount of Mg to the solution, while Ca dissolution lags. This implies that when altered basalt is utilized for CO 2 mineralization, the carbonation step may differ from that of fresh basalt, with predominant Mg carbonation followed by Ca carbonation. This rapid dissolution of Mg suggests that altered basalt is a promising feedstock for CO 2 mineralization. This study provides theoretical support for developing technologies to utilize altered basalt for carbon storage.

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Section: Resultsmentioning

confidence: 97%

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization

Wang,

Yagi,

Tamagawa

et al. 2024

ACS Omega

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“…Kanchanason et al (13) indicated that C-S-H precipitated at pH 10.4 was amorphous with a disordered structure. Analytical techniques such as X-ray diffraction (XRD) and thermogravimetric analysis (TGA) can identify mineralogical changes including formation of amorphous phases in lime-treated soils (14)(15)(16). Sayantan (10) successfully used thermogravimetric analysis to identify the formation C-S-H in lime-stabilized soils.…”

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Evaluating the Durability of Lime-Stabilized Soil Mixtures using Soil Mineralogy and Computational Geochemistry

Akula

Naik

Little

2021

Transportation Research Record: Journal of the Transportation R

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Lime stabilization is a common technique used to improve the engineering properties of clayey soils. The process of lime stabilization can be split into two parts. First, the mobilization and crowding of [Formula: see text] ions or [Formula: see text]molecules from hydrated lime at net negative surface charge sites on expansive clay colloids. Second, the formation of pozzolanic products including calcium-silicate-hydrate (C-S-H) because of reactions within lime-soil mixtures. The pozzolanic reaction is generally considered to be more durable, while the [Formula: see text] adsorption has been associated with more easily reversible consistency changes. This study offers a protocol to assess whether the stabilization process is dominated by durable C-S-H (pozzolanic) reactions or a combination of cation exchange and pozzolanic reactions. Expansive clays with plasticity indices >45% from a major highway project in Texas are the focus of lime treatment in this study. The protocol consists of subjecting lime-soil mixtures to a reasonable curing period followed by a rigorous but realistic durability test and investigating the quality and quantity of the pozzolanic reaction product. Mineralogical analyses using quantitative X-ray diffraction (XRD) and thermogravimetric analysis (TGA) indicates the formation of different forms of C-S-H. In addition, geochemical modeling is used to simulate the lime-soil reactions and evaluate the effect of pH on the stability of C-S-H. The results indicate C-S-H with Ca/Si ratio of 0.66 as most the stable form of C-S-H among other forms with Ca/Si ratio ranging from 0.66 to 2.25. The effect of reducing equilibrium pH on C-S-H is also evaluated. A reduction in pH favored dissolution of all forms of C-S-H indicating the need to maintain a pH ≥ 10.

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“…The GEM-Selektor program was developed to model geochemical reactions (10,11) based on Gibb's energy minimization and has been used extensively to simulate the hydration process in cement and fly ash and quantify the pozzolanic products (12)(13)(14)(15)(16). Little used thermodynamic modeling to evaluate ettringite formation in sulfate bearing soils (17).…”

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Evaluating the Long-Term Durability of Lime Treatment in Hydraulic Structures: Case Study on the Friant-Kern Canal

Akula

Hariharan

Little

et al. 2020

Transportation Research Record: Journal of the Transportation R

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The slopes along the Friant-Kern Canal were last treated in the 1970s with 4% quick lime to mitigate issues related to slope failure caused by expansive Porterville soils. The immediate benefits of lime treatment were well documented by the Bureau of Reclamation. However, questions remain over the long-term durability of lime-treated materials. In this study, we compare the engineering properties and changes in the soil mineralogy of treated and untreated sections to establish the effectiveness of lime after more than 40 years of performance. A geochemical model was developed using the GEM-Selektor program to simulate the geochemical reactions in the soil-lime system and predict stable pozzolanic products. The experimental results show a reduction in the plasticity index from 23 to 6 after lime treatment together with a tenfold increase in strength. Lime addition lowers the risk of volumetric expansion and erosion in soils from moderately high to very low. Further, a pH increase from 6.30 to 8.90 in lime-treated sections indicates that lime treatment continues to be effective. X-ray fluorescence analysis shows the presence of Ca2+ ions in quantities similar to the initial treatment dosage indicating negligible leaching of lime. The geochemical model provides evidence of the formation of pozzolanic products in the soil-lime system which was validated using thermogravimetry analysis. The performance history of the Friant-Kern Canal together with the findings of this study affirm the long-term durability of lime treatment on this project and strengthens the case for using lime in the repair of hydraulic structures.

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Thermodynamic Evaluation of Smectite Treated with Hydrogen Ion Stabilizer

Cited by 6 publications

References 25 publications

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization

Evaluating the Durability of Lime-Stabilized Soil Mixtures using Soil Mineralogy and Computational Geochemistry

Evaluating the Long-Term Durability of Lime Treatment in Hydraulic Structures: Case Study on the Friant-Kern Canal

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Thermodynamic Evaluation of Smectite Treated with Hydrogen Ion Stabilizer

Cited by 6 publications

References 25 publications

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO2-Rich Brine: Implications for CO2 Mineralization

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO2-Rich Brine: Implications for CO2 Mineralization

Evaluating the Durability of Lime-Stabilized Soil Mixtures using Soil Mineralogy and Computational Geochemistry

Evaluating the Long-Term Durability of Lime Treatment in Hydraulic Structures: Case Study on the Friant-Kern Canal

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Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization

Reactivity and Dissolution Characteristics of Naturally Altered Basalt in CO₂-Rich Brine: Implications for CO₂ Mineralization