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http://dx.doi.org/10.5345/JKIBC.2018.18.5.403

Carbonation Mechanism of Hydrated Cement Paste by Supercritical Carbon Dioxide  

Park, Jeong-Won (Department of Architectural Engineering, Pukyong National University)
Kim, Ji-Hyun (Multidisciplinary Infra-technology Research Laboratory, Pukyong National University)
Lee, Min-Hee (Department of Environmental Sciences, Pukyong National University)
Chung, Chul-Woo (Department of Architectural Engineering, Pukyong National University)
Publication Information
Journal of the Korea Institute of Building Construction / v.18, no.5, 2018 , pp. 403-412 More about this Journal
Abstract
Recently, needs for utilization of recycled aggregate have been increasing. However, its utilization has been limited due to its high alkalinity, which mostly came from the unremoved cement paste particles that were attached at the surface of recycled aggregate. Various efforts has been made to reduce its alkalinity by using $CO_2$, but currently available methods that uses $CO_2$ generate the problem with pH recovery. Considering the fact that supercritical $CO_2$ ($scCO_2$) can provide more rapid carbonation of cement paste than by normal $CO_2$, $scCO_2$ was utilized in this work. The reaction between $scCO_2$ and hydrated cement paste has been systematically evaluated. According to the results, it was found that powder type showed higher carbonation compared to that of cube specimens. It seems the carbonation by $scCO_2$ has occurred only at the surface of the specimen, and therefore still showed some amount of $Ca(OH)_2$ calcium aluminates after reaction with $scCO_2$. With powder type specimen, all $Ca(OH)_2$ was converted into $CaCO_3$. Moreover, additional calcium that came from both calcium aluminate hydrates and calcium silicate hydrates reacted with $scCO_2$ to form $CaCO_3$. After carbonation with $scCO_2$, the powder type specimen did not show pH recovery, but cube specimens did show due to the presence of portlandite.
Keywords
supercritical $CO_2$; recycled aggregate; cement paste; carbonation; portlandite; calcite; pH;
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Times Cited By KSCI : 3  (Citation Analysis)
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