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Effect of Na and Al on the phase composition and morphology of autoclaved calcium silicate hydrates
The hydrated materials were synthesized at 160-240 degree C in hydrothermal conditions. The series of samples with differing CaO/SiO2 ratios and doped with NaOH and Al(OH)3 (used as Na- and Al-bearing compounds) were produced, yielding materials consisting of the ill-crystallized calcium silicate hydrates and/or more crystalline calcium silicate phases. Generally, in the presence of sodium ions the acceleration of reactions leads to the formation of calcium-silicate-hydrate, which is an intermediate product for many well-defined phases that can appear in this system. A significant amount of sodium additive (although it accelerates the precipitation and to some extent the ordering of calcium-silicate-hydrate structure) seems to hinder the crystallization of well-developed, final phases, which are expected to be formed at assumed CaO-to-SiO2 ratios. The Ca-Na silicate hydrates are produced at significant sodium content (over 20% by weight), and at SiO2 content exceeding 50% by weight. When Al is added to the calcium hydroxide, silica, and NaOH water suspensions, the sodium aluminosilicate-analcite (Na(AlSi2O6).H2O) is detected, or the formation of more ordered CSH I (transformed subsequent to the tobermorite) is observed.
Effect of Na and Al on the phase composition and morphology of autoclaved calcium silicate hydrates
The hydrated materials were synthesized at 160-240 degree C in hydrothermal conditions. The series of samples with differing CaO/SiO2 ratios and doped with NaOH and Al(OH)3 (used as Na- and Al-bearing compounds) were produced, yielding materials consisting of the ill-crystallized calcium silicate hydrates and/or more crystalline calcium silicate phases. Generally, in the presence of sodium ions the acceleration of reactions leads to the formation of calcium-silicate-hydrate, which is an intermediate product for many well-defined phases that can appear in this system. A significant amount of sodium additive (although it accelerates the precipitation and to some extent the ordering of calcium-silicate-hydrate structure) seems to hinder the crystallization of well-developed, final phases, which are expected to be formed at assumed CaO-to-SiO2 ratios. The Ca-Na silicate hydrates are produced at significant sodium content (over 20% by weight), and at SiO2 content exceeding 50% by weight. When Al is added to the calcium hydroxide, silica, and NaOH water suspensions, the sodium aluminosilicate-analcite (Na(AlSi2O6).H2O) is detected, or the formation of more ordered CSH I (transformed subsequent to the tobermorite) is observed.
Effect of Na and Al on the phase composition and morphology of autoclaved calcium silicate hydrates
Nocun-Wczelik, W. (author)
Cement and Concrete Research ; 29 ; 1759-1767
1999
9 Seiten, 23 Quellen
Article (Journal)
English
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