Significance of water/solid ratio and temperature on the physico-mechanical characteristics of hydrating 4CaO.Al2O3.Fe2O3

Abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1007/BF00708268Journal of Materials Science, 11, 10, pp. 1893Science, 11, 10, pp. -1910Science, 11, 10, pp. , 1976 Significance of water-solic ratio and temperature on the physicomechanical characteristics of hydrating 4CaO.A12O3. Fe2O3 Ramachandran, V. S.; Beaudoin, J. J. Tetracalcium alumino-ferrite in paste form, at waterlsolid (WIS) ratios of 0.3,0.4,0.5 and 1 .O, and in pressed form at effective waterlsolid ratios of 0.13 and 0.08 has been hydrated for up to 45 days at temperatures of 23 and 80" C. Some prehydrated samples have also been subjected to autoclave treatment at 21 6" C. Of all the samples studied, that hydrated at a WIS = 0.1 3 at 80" C indicated the highest ratio of cubic phase to hexagonal phase; that hydrated at a WIS = 0.08 at 23" C showed the lowest. Thermograms gave evidence of the formation of hexagonal phases, although X-ray diffraction patterns did not. The specific surface area values depended on the degree of hydration and the nature of the product, autoclaved samples giving the lowest values. During the four days of hydration the specimen hydrated at 80" C expanded more than that hydrated at 23" C, but after that time the rates of expansion were reversed: that of the sample hydrated at 80" C was much lower than that of the sample hydrated at 23" C. Microstructural examination of the material formed at higher temperatures and lower waterlsolid ratios indicated a closely welded, continuous network of cubic phase. Such a structure yields a product of higher strength than that of a loose structure formed at higher waterlsolid ratios. A reasonably linear relation was found between porosity and logarithm of microhardness.

In-Situ Hydration Studies Using Multi-Angle Energy-Dispersive Diffraction

“…Its formation appears to be correlated with the loss of brownmillerite (~.1.3), from which it is known to hydrate, then remaining to the end of the autoclave cycle (90 min). It would appear that this is the first in-situ observation of this phase forming under these timescales and conditions and is consistent with published DTA evidence (Ramachandran & Beaudoin, 1976). 4.1.5.…”

Thermal Methods

“…Ramchandran and Beaudoin [117] hydrated C^AF with different w/c ratios at 23° and 80 C. DTA gave evidence of hexagonal phases (XRD did not). Collepardi and co-workers studied the hydration of Ct+AF extensively [118].…”

Characteristics of lime-silica fume mixtures

“…These hydrates are then transformed into a low-lime C-S-H with a lower water content up to 24 h. After 3 days of hydration, the molar ratios H20/SiO2 and CaO/SiO2 exhibit al- Table 2 Variation of H/S and C/S molar ratios for C-S-H formed of different ages of hydration of Mix II Differential thermal analysis (DTA) Figure 3 shows DTA curves of hydrated Mix I. They indicate a strong endothermic peak at 510~ due to the dehydration of calcium hydroxide subjected to a 30-min hydration, and a weak endothermic peak in the temperature range 115-230~ due to dehydration of poorly-crystallized C-S-H(I) and tobermorite gel [22,23]. The endothermic peak at 800~ is attributed to the decomposition of CaCO3, and the small exothermic peak at 900~ to the transition of the decomposed C--S-H(I) to wollastonite.…”