G. Parissakis

Investigation of the effect of Zn oxide on the formation of Portland cement clinker

Abstract Subject of this paper is to investigate the effect of ZnO during the sintering process of cement raw meal. The effect was studied by means of differential scanning calorimetry and X-ray diffraction. Besides, the rate of CaO consumption during the sintering of raw meals was measured. Final discussion concerns the action of the above oxide on raw material sintering and its incorporation in the phases of the clinker.

A mathematical model for the prediction of cement strength

Abstract In this paper a mathematical model for the prediction of Portland cement compressive strength after 2, 7 and 28 days is developed and the importance of chemical-mineralogical and fineness factors is pointed out. It is shown that the fineness is the predominant factor affecting the early strength while the chemical and mineralogical synthesis of the cement contribute to the strength development after 7 and 28 days. The 28 day strength of the cement is significantly affected by the distribution of the material in the size fractions

Investigation of the effect of Mo, Nb, W and Zr oxides on the formation of portland cement clinker

Abstract Subject of this paper is the effect of MoO3, Nb2O5, WO3 and ZrO2 on the properties of clinker originated from raw mixes containing the above oxides. This effect was studied by means of differential scanning calorimetry, X-Ray diffraction, optical and scanning electron microscopy. Final discussion concerns the action of the above oxides on raw material sintering and the resulting effects on the microstructure and properties of produced clinker.

A study on the burnability and the phase formation of PC clinker containing Cu oxide

Abstract Subject of this paper is to investigate the effect of CuO on the burnability of the cement raw mix and on the phase formation of the clinker. The effect was studied by means of differential scanning calorimetry, X-ray diffraction and optical microscopy. Besides, the rate of fCaO consumption during the sintering of raw meals was measured. As it is concluded the presence of the CuO in cement raw mix promotes the combination of the free lime, especially in the temperature range between 1000 and 1300 °C. It also favors the formation of alite and belite at lower temperatures. Furthermore, CuO lowers the temperature of the sintering reactions.

On the hydration of MgO in cement pastes hydrated up to eight years

Abstract The present work extends the knowledge on the behaviour of high magnesia cements, pure or with pozzolanic additives cured for 8 years in potable water at 18+2°C. For this purpose, clinker containing 10% MgO was prepared in an appropriate furnace. The raw materials used were all of industrial origin. Four cements were prepared by cogrinding clinker with gypsum and the following pozzolanic materials: Santorin Earth (S.E.), Fly Ash I (F.A.I.), Fly Ash II (F.A.II) and Fly Ash III (F.A.III), in a proportion of 30%. The Mg(OH) 2 produced during the hydration of the above cements was determined quantitatively by thermogravimetric method, while the hydration phenomena were studied by X.R.D. It is concluded that when clinker containing ca. 10% MgO is coground with a good pozzolan, the hydration of MgO reaches a limited value at the age of ca. 6 years. The percentage of hydrated MgO permits the safe use of these cements, as for the long term unsoundness due to MgO hydration.

The combined action of Mg2+ and Cl− ions in cement pastes

Abstract In order to study the phenomenon of seawater attack on hydrated cement components, we focused our interest on the combined action of Mg2+ and Cl− ions on hydrated cement pastes. Thus, cement pastes were prepared from portland cement and its mixture with 30% pozzolan (Santorin Earth). These pastes were cured in baths of varied concentrations of Mg2+ and Cl− ions and stored in 18 ± 2°C. The hydration phenomena were studied in these cement pastes, by XRD and SEM.

Hydration and strength development of cements produced from raw mixes containing MoO3, Nb2O5, WO3 and ZrO2

Abstract The purpose of this paper is to investigate the effects of MoO 3 , Nb 2 O 5 , WO 3 and ZrO 2 on the hydration process and on the mechanical properties of cement. The above oxides were added separately to cement raw mixes and their influence on hydration of derived cements was studied by means of thermal analysis and X-Ray diffraction. Additionally, compressive strength and setting time were measured.

DTA-TG study on the Ca(OH)2 - pozzolan reaction in cement pastes hydrated up to three years

Abstract In order to study the way in which Santorin earth (pozzolan) acts during its hydration with portland cements and specifically, the rates of its action and its optimum content, the amount of Ca(OH) 2 derived during the hydration has been quantitatively determined, by means of thermogravimetry. Thus, cement pastes have been prepared with mixtures of portland cement containing proportions of Santorin earth up to 40% of various finenesses. These pastes were cured in water up to three years.

A mathematical model for the control of cement setting using calcium chloride as accelerator

Abstract In this paper a mathematical model for the control of Portland cement setting, using CaCl2 as accelerator, is developed and the importance of chemicalmineralogical and fineness factors is pointed out. It is shown that the ratio C 3 A C 4 AF as well as the SO3 content are the predominant factors affecting the setting, while the fineness parameters, the specific surface and the fraction 3–32μm, also influence the setting time. The effect of fineness parameters is more pronounced upon the final setting.