It has been shown that the reactivity of calcium aluminate phases such as CaO . Al2O3 (CA*), CaO . 2Al(2)O(3) (CA(2)), and of Al2O3 (A) can be influenced by a thermal treatment of the ground products at temperatures in the range from 300 up to 800 degrees C. The effect of this tempering process differs for the three compounds. For CA a homogenization of reactivity can be reached. This effect can be observed with calorimetry evaluating the time at which the so called second peak occurs. For CA(2) the hydraulic activity may distinctly diminish. In the case of aluminas a different hydration behaviour in mixes with CA was observed influencing the composition of hydrated phases. Reasons for these effects such as changes of defect concentration and/or special surface sites (e.g. OH-groups) will be discussed.

Measurement of the conductivity of stirred and diluted suspensions of fondu cement hydrated in water at different temperatures indicates that the duration of the induction period that occurs before the massive precipitation of hydrates passes through a maximum at 27°C. The temperature at which the maximum occurs depends upon the nucleation rates of CAH10 and AH3: the CAH10 nucleation rate is expected to decrease with temperature whereas the AH3 nucleation rate is expected to increase. Thus, one passes from an induction period controlled by the CAH10 nucleation rate to an induction period controlled by AH3 at the temperature that induces the maximum retardation of the hydration. This mechanism explains why lithium salts can reduce or even remove this maximum of retardation.

Measuring the conductivity of stirred and diluted suspensions of Fondu cement enables the action of admixtures on the dissolution and induction periods to be determined. These events occur before the massive precipitation of hydrates leading to setting of the paste. These new results, compared to those obtained on paste, are useful in determining the mechanisms of interaction between Fondu cement hydration and admixtures. The behaviour of lithium and sodium salts is a result of the sum of the interactions due to their cationic and anionic parts. Experiments with lithium salts seem to be compatible with the hypothesis of an induction period kinetically controlled by a nucleation and growth process of AH3 at 2°C

The influence of alumina on the hydration of monocalcium aluminate (CA1) has been studied at 15, 20 and 25-degrees-C using differential calorimetric analysis and X-ray powder diffraction. The hydration of CA in the presence of alumina has been accelerated very strongly at all temperatures in contrast to the hydration of pure CA where an anomalous setting behaviour has been observed above 22-degrees-C. In the case of the mixtures C2AH8 is the main hydration product at 20 and 25-degrees-C, i.e. in the range of the anomalous hydration behaviour of pure CA. During the hydration of CA and CA/A mixtures considerable amounts of X-ray amorphous products have been formed.

ChemInformVolume 20, Issue 4 Physical Inorganic Chemistry ChemInform Abstract: Change of the Microstructure During the Hydration of Monocalcium Aluminate at 50 °C. A. RETTEL, A. RETTEL Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorR. TRETTIN, R. TRETTIN Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorW. GESSNER, W. GESSNER Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this author A. RETTEL, A. RETTEL Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorR. TRETTIN, R. TRETTIN Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorW. GESSNER, W. GESSNER Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this author First published: January 24, 1989 https://doi.org/10.1002/chin.198904025Citations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume20, Issue4January 24, 1989 RelatedInformation

AbstractDer Verlauf der Hydratation des Monocalciumaluminats bei 50°C ist gekennzeichnet durch Perioden unterschiedlicher Reaktionsgeschwindigkeit. Durch Verfolgung der Oberflächen‐ und Wärmeentwicklung, des Umsatzes sowie durch Analyse der entstehenden Lösungsphase wird gezeigt, daß dieses Verhalten in der Anfangsphase der Reaktion mit der Ausbildung einer primären Reaktionsschicht auf der Oberfläche des CaO · Al2O3 erklärbar ist. Zu späteren Zeiten wird die Reaktionsgeschwindigkeit durch Veränderungen der Mikrostruktur der das CaO · Al2O3‐Korn umschließenden Hülle der Hydratationsprodukte beeinflußt, die in Umwandlungs‐ und Kristallisationsvorgängen begründet sind.

ChemInformVolume 18, Issue 35 Physical Inorganic Chemistry ChemInform Abstract: The Course of Hydration of CaO·Al2O3 in the Primary States R. TRETTIN, R. TRETTIN Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorA. RETTEL, A. RETTEL Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorW. GESSNER, W. GESSNER Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this author R. TRETTIN, R. TRETTIN Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorA. RETTEL, A. RETTEL Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this authorW. GESSNER, W. GESSNER Zentralinst. Anorg. Chem., Akad. Wiss. DDR, DDR-1199 Berlin-AdlershofSearch for more papers by this author First published: September 1, 1987 https://doi.org/10.1002/chin.198735024Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume18, Issue35September 1, 1987 RelatedInformation

AbstractDurch Verfolgung der Oberflächenentwicklung bei der Reaktion von CaO · Al2O3 mit Wasser, die chemische Analyse der entstehenden Lösungsphase sowie durch differentialcalorimetrische Untersuchungen wird gezeigt, daß der primäre Verlauf der Hydratation durch die Ausbildung und Veränderung einer Reaktionsschicht auf der Oberfläche des Monocalciumaluminats erklärbar ist.

AbstractEs wurde der Einfluß der Temperatur auf die Hydratation des Monocalciumaluminats, CaO · Al2O3, mittels der Differentialcalorimetrie, der Bestimmung der zeitlichen Änderung der aus 1H‐NMR‐Messungen zu ermittelnden Spin‐Gitter‐Relaxationszeit T1 der Protonen sowie durch röntgenographische Charakterisierung der entstehenden Hydratationsprodukte untersucht. Es wird gezeigt, daß die Hydratation im Temperaturbereich zwischen 4 und 83°C nach mindestens drei, mit steigender Temperatur einander ablösenden, unterschiedlichen Prinzipien erfolgt.

AbstractFür das Monocalciumaluminat CaO‐Al2O3 (als Zement‐Hauptklinkerphase) wurde die Hydratation, die die Festigkeitsentwicklung von mit Tonerdezement gebundenen hitzebeständigen Betonen wesentlich bestimmt, mittels der Differentialcalorimetrie, der zeitlichen Änderung der aus 1H‐NMR‐Messungen zu ermittelnden Spin‐Gitter‐ Relaxationszeit T1 der Protonen sowie durch röntgenographische Charakterisierung der entstehenden Hydratationsprodukte untersucht.