Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Hydration of Portland cement in the presence of aluminum-containing setting accelerators
Portland cement hydration in the presence of two different aluminum-containing compounds, highly dispersed amorphous Al(OH)3 and aqueous solution of aluminum hydroxosulfate Al(OH)1.78(SO4)0.61, was studied by solid-state Al and Si NMR spectroscopy. The aluminum hydroxosulfate solution as accelerator of cement paste setting acts more efficiently than amorphous Al(OH)3, which is due to more intense formation of ettringite. In small amounts (-0.5 wt % counting on Al2O3), both additives accelerate the hydration of silicate phases of the cement and enhance the strength of cement stone relative to the control specimen. An increase in the A1(OH)3 dosage (-1.5% counting on Al2O3), along with acceleration of cement paste setting, practically fully suppresses the hydration of Portland cement in the early period and leads to a decrease in the 24-h strength of the cement stone, which is several times lower than that of the control specimens. The decelerating effect of aluminum hydroxosulfate is considerably weaker than that of Al(OH)3 at equivalent dosage. The strength of the cement stone with this additive at the age of 24 h is higher than that of the control specimens, apparently because of the effect of ettringite participating in the structure formation along with C-S-H gel. The deceleration of the cement hydration in the presence of large amounts of highly active aluminium-containing additives is due to formation (under the conditions of deficiency of SO42- and Ca2+ ions) of the aluminosilicate gel blocking the silicate phases of the cement clinker. This deficiency is more pronounced with Al(OH)3 and less pronounced with aluminum hydroxosulfate, which is a source of sulfate ions.
Hydration of Portland cement in the presence of aluminum-containing setting accelerators
Portland cement hydration in the presence of two different aluminum-containing compounds, highly dispersed amorphous Al(OH)3 and aqueous solution of aluminum hydroxosulfate Al(OH)1.78(SO4)0.61, was studied by solid-state Al and Si NMR spectroscopy. The aluminum hydroxosulfate solution as accelerator of cement paste setting acts more efficiently than amorphous Al(OH)3, which is due to more intense formation of ettringite. In small amounts (-0.5 wt % counting on Al2O3), both additives accelerate the hydration of silicate phases of the cement and enhance the strength of cement stone relative to the control specimen. An increase in the A1(OH)3 dosage (-1.5% counting on Al2O3), along with acceleration of cement paste setting, practically fully suppresses the hydration of Portland cement in the early period and leads to a decrease in the 24-h strength of the cement stone, which is several times lower than that of the control specimens. The decelerating effect of aluminum hydroxosulfate is considerably weaker than that of Al(OH)3 at equivalent dosage. The strength of the cement stone with this additive at the age of 24 h is higher than that of the control specimens, apparently because of the effect of ettringite participating in the structure formation along with C-S-H gel. The deceleration of the cement hydration in the presence of large amounts of highly active aluminium-containing additives is due to formation (under the conditions of deficiency of SO42- and Ca2+ ions) of the aluminosilicate gel blocking the silicate phases of the cement clinker. This deficiency is more pronounced with Al(OH)3 and less pronounced with aluminum hydroxosulfate, which is a source of sulfate ions.
Hydration of Portland cement in the presence of aluminum-containing setting accelerators
Brykov, A.S. (Autor:in) / Vasilev, A.S. (Autor:in) / Mokeev, M.V. (Autor:in)
Russian Journal of Applied Chemistry ; 86 ; 793-801
2013
9 Seiten, 6 Bilder, 2 Tabellen, 16 Quellen
Aufsatz (Zeitschrift)
Englisch
Influence of Setting Accelerators on Chemical Shrinkage of Portland Cement
| British Library Conference Proceedings | 2001
Hydration of Portland cement in presence of silica fume
| Online Contents | 2010
Early hydration behaviour of Portland cement containing montmorillonogypsum
| Tema Archiv | 1996