ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
The Conditions of Ettringite Formation by the Reaction of a Blast Furnace Slag with Aqueous Alkaline Solutions
Aya HarashimaKimihisa Ito
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2016 Volume 56 Issue 10 Pages 1738-1745

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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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© 2016 by The Iron and Steel Institute of Japan
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