In order to clarify the distribution of titania in the phases of the portland cement clinker, 0, 5, 10 and 15% of 3CaO⋅2TiO
2 were added to the model clinker which was composed of 35% of 3CaO⋅SiO
2, 35% of 3CaO⋅SiO
2, 15% of 3CaO⋅Al
2O
3 and 15% of 4CaO⋅Al
2O
3⋅Fe
2O
3 in weight, and the samples were heated between 1350° and 1500°C. They were then examined by means of X-ray diffraction analysis, microscopic observation and electoron probe microanalysis.
The following results were obtained;
1) Titania replaces a part of silica in 3CaO⋅SiO
2 and 2CaO⋅SiO
2 phases and also the liquid phase during heating, and the degree of replacement is independent of the concetration of Al
2O
3 and Fe
2O
3 in each phase.
2) The solubility limits of Al
2O
3, Fe
2O
3 and TiO
2 are approximately 1, 1 and 3% respectively in 3CaO⋅SiO
2 phase, and 2, 2 and 6% or more in 2CaO⋅SiO
2 phase.
3) As a result of replacement of SiO
2 by TiO
2, 3CaO⋅SiO
2 phase decreases while 2CaO⋅SiO
2 phase increases, due to insufficient CaO content when TiO
2 is added in the form of 3CaO⋅2TiO
2 to the clinker.
4) The grain size of 3CaO⋅SiO
2 phase increases by the addition of 3CaO⋅2TiO
2.
5) Especially in the liquid phase most of SiO
2 can be replaced by TiO
2.
6) Titania in the liquid phase concentrates on cooling in the light interstitial or ferrite phase rather than in the dark interstitial or aluminate phase.
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