Researches on the Complete Hydrate of Portland Cement Compounds
1960 Volume 68 Issue 775 Pages 180-190
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1960 Volume 68 Issue 775 Pages 180-190
Complete hydration products of portland cement compounds and their mixtures with or without gypsum produced by ball mill hydration at 20°C, W/C=80%, were investigated by X-ray diffraction analysis, infra-red absorption spectrum, differential thermal analysis, electron microscopic observation and chemical analysis. The results obtained are summerized as follows:-
(1) Complete hydrate of 3CaO⋅SiO2 was identified as Afwillite Ca3(SiO3OH)2⋅2H2O by X-ray diffraction and differential thermal analysis, but calculated composition of this hydrate was C1.68SH1.26, based on the chemical composition of initial synthesized 3CaO⋅SiO2, loss on ignition at 900°C and the quantity of liberated Ca(OH)2.
The Ca(OH)2 liberated from 3CaO⋅SiO2 during the process of hydration was extracted after Lerch-Bogue method until (001) reflection of Ca(OH)2 was not recognized by X-ray diffraction analysis, so it is considered that both amorphous and crystaline Ca(OH)2 were measured. The authors supposed that the difference of composition of Afwillite and complete hydrate of 3CaO⋅SiO2 was not, as Brunauer et al say, caused by missing the amorphous Ca(OH)2, but the essential property of hydrate having various composition within suitable range. Infra-red absorption spectrum shows the existence of hydrogen bond in Afwillite structure.
X-ray diffraction pattern of complete hydrate of β-2CaO⋅SiO2 contained diffraction lines of Tobermorite.
(2) The complete hydrate of 3CaO⋅Al2O3 was cubic crystal of 3CaO⋅Al2O3⋅6H2O, while that of 4CaO⋅Al2O3⋅Fe2O3 was the solid solution of 3CaO⋅Al2O3⋅6H2O-3CaO⋅Fe2O3⋅6H2O (lattice constant a=12.614 Å) having approximate composition of 3CaO⋅0.8Al2O3⋅0.2Fe2O3⋅6H2O.
Infra-red absorption sprctra of complete hydrate of 3CaO⋅Al2O3 and 4CaO⋅Al2O3⋅Fe2O3 suggest some difference about combined water between cubic calcium aluminate hydrate, solid solution of 3CaO⋅Al2O3⋅6H2O-3CaO⋅Fe2O3⋅6H2O and calcium silicate hydrate.
(3) The complete hydrate of 3CaO⋅SiO2 with gypsum and 3CaO⋅SiO2, 3CaO⋅Al2O3 mixture with or without gypsum were somewhat different from the complete hydrate of 3CaO⋅SiO2 (Afwillite).
In the complete hydrate of 3CaO⋅SiO2 and CaSO4⋅2H2O mixture, CaSO4⋅2H2O were completely extracted by saturated lime water, while the complete hydrate of 3CaO⋅SiO2-3CaO⋅Al2O3 mixture showed X-ray diffraction patterns and differential thermal analysis curves of 3CaO⋅Al2O3⋅6H2O besides calcium silicate hydrate. So it is not considered that CaSO4⋅2H2O and 3CaO⋅Al2O3 made solid solution or complex compound with calcium silicate hydrate.
From these results, the authors supposed that the reason of the formation of new calcium silicate hydrate is the difference of the equilibrium of liquid phase produced during the process of hydration.
