The conditions of ettringite formation by the reaction of a blast furnace slag with aqueous alkaline solutions

Aya Harashima, Kimihisa Ito

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    Blast furnace (BF) slags have been utilized in cement, concrete aggregate, roadbed materials, and earthwork materials. If an appropriate control of the elution and compound formation is developed under severer environmental conditions, their usage would be more diverse. Because the chemical composition of BF slag is similar to that of Portland cement, the possibility of ettringite (3CaO·Al2O3·3CaSO4·32H2O) formation from BF slag following a mechanism similar to that of cement hydration might be possible under a wet alkaline environment. Therefore, the effect of an alkaline solution on ettringite formation from BF slags was investigated by slag-leaching experiments and thermodynamic calculations using PHREEQC. The formation of ettringite was observed only for the high pH solutions in the experiments, whereas its thermochemical possibility from the air-cooled BF slags was always expected by the calculation. The kinetic analysis showed that the dissolution of alumina from the slag may control the whole reaction rate. The mixing of granulated BF slag with air-cooled ones tended to enhance the ettringite formation. Furthermore, a technique for removing the ettringite formed in the slag was also developed.

    Original languageEnglish
    Pages (from-to)566-573
    Number of pages8
    JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
    Volume101
    Issue number11
    DOIs
    Publication statusPublished - 2015

    Fingerprint

    slags
    blasts
    Slags
    furnaces
    cements
    Cements
    ettringite
    Concrete aggregates
    elution
    Aluminum Oxide
    air
    Portland cement
    leaching
    Air
    Hydration
    Leaching
    Reaction rates
    hydration
    dissolving
    chemical composition

    Keywords

    • Alkaline solution
    • Blast furnace slag
    • Ettringite formation
    • PHREEQC
    • Reaction kinetics
    • Slag-leaching
    • Thermodynamic calculation

    ASJC Scopus subject areas

    • Materials Chemistry
    • Metals and Alloys
    • Condensed Matter Physics
    • Physical and Theoretical Chemistry

    Cite this

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    abstract = "Blast furnace (BF) slags have been utilized in cement, concrete aggregate, roadbed materials, and earthwork materials. If an appropriate control of the elution and compound formation is developed under severer environmental conditions, their usage would be more diverse. Because the chemical composition of BF slag is similar to that of Portland cement, the possibility of ettringite (3CaO·Al2O3·3CaSO4·32H2O) formation from BF slag following a mechanism similar to that of cement hydration might be possible under a wet alkaline environment. Therefore, the effect of an alkaline solution on ettringite formation from BF slags was investigated by slag-leaching experiments and thermodynamic calculations using PHREEQC. The formation of ettringite was observed only for the high pH solutions in the experiments, whereas its thermochemical possibility from the air-cooled BF slags was always expected by the calculation. The kinetic analysis showed that the dissolution of alumina from the slag may control the whole reaction rate. The mixing of granulated BF slag with air-cooled ones tended to enhance the ettringite formation. Furthermore, a technique for removing the ettringite formed in the slag was also developed.",
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