Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements
Journal Article
·
· Cement and Concrete Research
- Brookhaven National Lab., Upton, NY (United States). Energy Efficiency and Conservation Div.
Sodium metaphosphate-modified fly ash/calcium aluminate blend (SFCB) cements were prepared by autoclaving for 1 day at 300 C and their resistance was evaluated in a highly concentrated Na{sub 2}CO{sub 3} solution at 300 C. The hydroxyapatite and analcime phases formed in the autoclaved SFCB cements played an essential role in conferring resistance to the degradation of cements caused by alkali carbonation. Although the carbonating reaction of the analcime phase led to the formation of cancrinite, this analcime cancrinite transformation did not show any influence on the changes in the mechanical and physical properties of the cements. Additionally, there was no formation of the water-soluble calcium bicarbonate in the cements exposed for 28 days. Contrarily, the conventional class G cement systems were very vulnerable to a hot alkali carbonation. The major reason for the damage caused by carbonation of the cements was the fact that the xonotlite phase formed in the 300{degree} autoclaved cements was converted into two carbonation products, calcite and pectolite. Furthermore, the reaction between calcite and carbonic acid derived from Na{sub 2}CO{sub 3} led to the formation of water-soluble calcium bicarbonate, thereby causing the alteration of dense structures into porous ones and the loss of strength of cements.
- OSTI ID:
- 404581
- Journal Information:
- Cement and Concrete Research, Journal Name: Cement and Concrete Research Journal Issue: 11 Vol. 26; ISSN CCNRAI; ISSN 0008-8846
- Country of Publication:
- United States
- Language:
- English
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