A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements
SFCB (sodium metaphosphate-modified fly ash/calcium aluminate blend) cements were prepared by autoclaving for 1 day at 300 deg C and their resistance was evaluated in a highly concentrated Na2CO3 solution at 300 deg 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 deg C autoclaved cements was converted into two carbonation products, calcite and pectolite. Furthermore, the reaction between calcite and carbonic acid derived from Na2CO3 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.
Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements
SFCB (sodium metaphosphate-modified fly ash/calcium aluminate blend) cements were prepared by autoclaving for 1 day at 300 deg C and their resistance was evaluated in a highly concentrated Na2CO3 solution at 300 deg 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 deg C autoclaved cements was converted into two carbonation products, calcite and pectolite. Furthermore, the reaction between calcite and carbonic acid derived from Na2CO3 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.
Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements
Alkalicarbonatreaktionen von natriummetaphosphatmodifizierten hydrothermalen Zementen aus Flugasche-Calciumaluminatmischungen bei hoher Temperatur
Sugama, T. (author)
Cement and Concrete Research ; 26 ; 1661-1672
1996
12 Seiten, 7 Bilder, 1 Tabelle, 10 Quellen
Article (Journal)
English
Carbonat , Flugasche , Flugaschenzement , Zement , hydraulisches Bindemittel , Natriumcarbonat , Phosphat , alkalihaltiger Phosphat , Autoklavierung , Calciumaluminatbinder , Tonerdeschmelzbeton , hydraulischer Zement , Calciumsilicathydrat , Phasenzusammensetzung , Phasenumwandlung , Hydroxylapatit , Zerfall , mechanische Eigenschaft , physikalische Eigenschaft , Calcit , Tonerdezement
| British Library Online Contents | 1996
Hydrothermal treatment of calcium aluminate-fly ash-sodium metaphosphate cements
| Online Contents | 1997