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Some physical properties of anhydrous and hydrated Brownmillerite doped with NaF
Different samples of Brownmillerite (the ferrite phase of cement clinker) doped with 0, 1 or 3 wt.% NaF were prepared. At first, the oxide mixture of Brownmillerite was prepared according to the following composition: 4 mol CaO, 1 mol Al2O3 and 1 mol Fe2 O3 in addition to 1 or 3 wt.% NaF. Each mixture was mixed very well, introduced into an electric furnace at 1300 degree C for 1 h in a platinum crucible, and then quenched in air. The product was divided into four portions mixed with 40 wt.% distilled water to form Brownmillerite paste, except for one portion which was left dry. Each paste was molded into two molds; after 24 h, they were immersed in a distilled water and withdrawn after 1 or 3 days of hydration, respectively. The pastes were ground again. The anhydrous powders of Brownmillerites and the hydrated samples were prepared for a.c. conduction measurements by pressing it to be in pellets form. The two surfaces of each pellet were coated with silver paste. The a.c. conductivity and dielectric constant for different samples were measured using four-probe method. The data was collected from 320 up to 670 K. Mossbauer spectra and X-ray diffraction patterns were measured for each sample (anhydrous and hydrated) to confirm the formation of Brownmillerite, identify the iron states and the magnetic properties. The results showed that NaF addition to Brownmillerite expedites the hydration reaction rate. The superparamagnetic relaxation, which appeared in the anhydrous Brownmillerite spectra due to the small particle size, decreases with increasing the hydration time. Also, the Fe3+(Oh) state increases while Fe3+(Td) decreases with the time of hydration. The a.c. conductivity value at fixed frequency for anhydrous and hydrated samples was found to increase with NaF addition. The a.c. conductivity and Mossbauer measurements can be used as good tools to verify the purity of Brownmillerite phase and, accordingly, the purity of cement.
Some physical properties of anhydrous and hydrated Brownmillerite doped with NaF
Different samples of Brownmillerite (the ferrite phase of cement clinker) doped with 0, 1 or 3 wt.% NaF were prepared. At first, the oxide mixture of Brownmillerite was prepared according to the following composition: 4 mol CaO, 1 mol Al2O3 and 1 mol Fe2 O3 in addition to 1 or 3 wt.% NaF. Each mixture was mixed very well, introduced into an electric furnace at 1300 degree C for 1 h in a platinum crucible, and then quenched in air. The product was divided into four portions mixed with 40 wt.% distilled water to form Brownmillerite paste, except for one portion which was left dry. Each paste was molded into two molds; after 24 h, they were immersed in a distilled water and withdrawn after 1 or 3 days of hydration, respectively. The pastes were ground again. The anhydrous powders of Brownmillerites and the hydrated samples were prepared for a.c. conduction measurements by pressing it to be in pellets form. The two surfaces of each pellet were coated with silver paste. The a.c. conductivity and dielectric constant for different samples were measured using four-probe method. The data was collected from 320 up to 670 K. Mossbauer spectra and X-ray diffraction patterns were measured for each sample (anhydrous and hydrated) to confirm the formation of Brownmillerite, identify the iron states and the magnetic properties. The results showed that NaF addition to Brownmillerite expedites the hydration reaction rate. The superparamagnetic relaxation, which appeared in the anhydrous Brownmillerite spectra due to the small particle size, decreases with increasing the hydration time. Also, the Fe3+(Oh) state increases while Fe3+(Td) decreases with the time of hydration. The a.c. conductivity value at fixed frequency for anhydrous and hydrated samples was found to increase with NaF addition. The a.c. conductivity and Mossbauer measurements can be used as good tools to verify the purity of Brownmillerite phase and, accordingly, the purity of cement.
Some physical properties of anhydrous and hydrated Brownmillerite doped with NaF
Hassaan, M.Y. (author) / El Desoky, M.M. (author) / Salem, S.M. (author) / Yousif, A.A. (author)
Cement and Concrete Research ; 33 ; 697-702
2003
6 Seiten, 23 Quellen
Article (Journal)
English
Some physical properties of anhydrous and hydrated Brownmillerite doped with NaF
| Online Contents | 2003
Some physical properties of anhydrous and hydrated Brownmillerite doped with NaF
| British Library Online Contents | 2003
| Engineering Index Backfile | 1935
Some physical properties of hydrated cements
| Engineering Index Backfile | 1930
Some physical properties of hydrated cements
| Engineering Index Backfile | 1930