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Ipavec A.,Salonit Anhovo Building Materials Joint Stock Co. | Gabrovsek R.,Slovenian National Institute of Chemistry | Vuk T.,Salonit Anhovo Building Materials Joint Stock Co. | Kaucic V.,Slovenian National Institute of Chemistry | And 2 more authors.
Journal of the American Ceramic Society | Year: 2011

It has been an established fact that finely ground calcium carbonate represents to a certain extent an active component during the hydration of Portland cement and the formation of calcium monocarboaluminate has been confirmed many times. Additionally, the formation of calcium hemicarboaluminate, as another possible compound, has been mentioned. There is, however, lack of specific information regarding these two compounds: there has been no experimental data on their hydration time-dependent formation, their interrelations, and their amount in a hardened cement paste. This paper describes the time-related formation of hemicarboaluminate and monocarboaluminate and reports for the first time in the literature the conversion of hemicarboaluminate into monocarboaluminate on the basis of X-ray diffraction by following the content of the latter using the Rietveld method. Hemicarboaluminate appears at early hydration times in calcite-containing Portland cement, even in the presence of large amounts of calcium carbonate. As the hydration progresses, a gradual conversion of hemicarboaluminate into monocarboaluminate occurs. The only detectable AFm-type compound present in well-hydrated cement is calcium monocarboaluminate. © 2010 The American Ceramic Society. Source


Ipavec A.,Salonit Anhovo Building Materials Joint Stock Co. | Vuk T.,Salonit Anhovo Building Materials Joint Stock Co. | Gabrovsek R.,Slovenian National Institute of Chemistry | Kaucic V.,Slovenian National Institute of Chemistry
Cement and Concrete Research | Year: 2013

Chloride binding into ten hydrated cement binders containing limestone and different pozzolanic materials was systematically investigated. The results showed that the amount of bound chloride in pozzolan-blended cements strongly depended on the content of aluminum in the binder. The presence of limestone in cement significantly decreased chloride binding capacity under the condition of common alkalinity (pH ≈ 13.5). The effect of limestone seemed to be related to decreased ability of chloride binding into carboaluminate phases that formed during the hydration of calcium carbonate-containing cement. Alkalinity of the synthetic pore solution generally influenced the course of binding with the effect being more pronounced at lower chloride concentrations. The presence of alkalis hindered the formation of chloroaluminate phases and decreased the chloride binding capacity. Lowering of the temperature resulted in a decreased amount of bound chloride. The reversibility of chloride binding was largely maintained under the condition of constant alkalinity. © 2013 Elsevier Ltd. Source

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