Mechanisms of cement hydration

Raman spectroscopy studies of alkali and alkaline earth silicate glasses and melts are reviewed, and the major Raman bands observed are summarized. To realize the full potential of Raman spectroscopy will require a detailed understanding of their vibrational properties in relation to structure. A number of vibrational calculations have been carried out to address this problem. These are briefly summarized, and some limitations of the method are noted. Systematic variations in bulk properties are examined for viscosity and the immiscibility behavior.

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Structural studies of silicate glasses and melts—applications and limitations of Raman spectroscopy

http://blogs.cae.tntech.edu/hydration-kinetics/files/2009/08/julliland_04_quebec_hydration-mechanism.pdf

Dissolution theory applied to the induction period in alite hydration

Raman spectroscopic measurements in borate glasses have been reviewe. The review shows that the technique is useful in identifying the structural groups present in the borate on the basis of the Krogh-Moe hypothesis. Vitreous B2O3 and alkali borates are extensvvely studied and a satisfactory assignment of bands is possible by a careful consideration of the literature. A cation effect on the borate netwoork is observed. Availaable measurements on binary borates other than alkali borates and on ternary borates are limited and more work is required to identify the structural modifications that take place with composition. Mixed alkali effect is reported only lithium-caesium borade and shows the formation of non-bridging oxygens, destroying the six-membered rings when Li2O is replaced by Cs2O. Fast ionic glasses (alkali borates containing alkali halides) yield the same Raman spectra as the alkali borates, except when the alkali is a fluoride.

Raman spectral studies of borate glasses

The infrared spectra of zinc-doped lead borate glasses (10–30 mol% ZnO) were measured over a continuous spectral range (400–4000 cm−1) in an attempt to study their structure systematically. No boroxol ring formation was observed in the structure of these glasses. The formation of Zn in tetrahedral coordination was not observed. The conversion of three-fold to four-fold coordinated boron took place.

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Infrared spectra of zinc doped lead borate glasses

Raman spectra of alkali and alkaline earth borosilicate glasses are reported. These spectra are used to discuss the molecular structure of the glasses. The influence of Al 2 O 3 additions on the structure of borosilicate glass is also discussed. It is shown that the same type of groups are present in borosilicate glasses as in borate and silicate glasses. The presence of large borate groups such as tetraborate and metaborate groups is strongly suggested by the Raman spectra. It appears that boron ions are hardly taken up in the silicon-oxygen network. Our results suggest that the region of phase separation is larger than the region presently acknowledged.

The structure of borosilicate glasses studied by Raman scattering

The results of following the quantities of free Ca(OH)2 in tricalcium silicate (3CaO.SiO2) of portland cement during the hydration and the influence of the presence of free CaO on the reaction are in agreement with the hypothesis of Stein and Stevels with regard to the hydration of 3CaO.SiO2 (CA 61: 9280g). The hydration process was studied by ir spectra and the electron microscope. When 3CaO.SiO2 comes in contact with the water, the hydrate (I) which is not distinguished from the 3CaO.SiO2 by an electron microscope is formed close to the 3CaO.SiO2 surface. Hydrate I has a very high CaO/SiO2 ratio (.apprx.3:1 moles) and strongly retards further hydration. Hydrate I is converted to a 2nd hydrate (II) which retards the hydration reaction less and has a lower CaO/SiO2 ratio. Once nuclei of hydrate II are formed the conversion takes place with a higher velocity and hydrate II converts to hydrate (III), the poorly crystd. hydrate with a CaO/SiO2 mole ratio >1.5 (tobermorite gel). The transition from hydrate I to hydrate II is accelerated by a decrease in the Ca2+ and OH- concn. in the water phase under which the formation of hydrate II nuclei is accelerated. [on SciFinder (R)]

Hydration of tricalcium silicate

Raman scattering measurements of silicate glasses and compounds

The critical cooling rate of a substance is the minimum linear rate at which its melt must be cooled to prevent crystallization entirely. In a number of systems this critical cooling rate has proved to be a useful quantitative experimental measure of the tendency to glass formation. The present paper describes a method of deriving theoretical values of the critical cooling rate from classical nucleation kinetics. In general, the calculated values show the correct tendency to glass formation.

Nucleation kinetics and critical cooling rate of glass-forming liquids

Glasses may be defined as solid systems characterized by the absence of short time fluidity and having structures characterized by the absence of long range order. This definition is rather vague; nevertheless it expresses that the glasses do show some fluidity (certainly at longer observation times) and that their structures are definitely not completely random. In attempts to describe these features in a more quantitative way, it is useful to define two parameters, the Repeatibility Number and the Deborah Number. The former is a parameter giving the degree of order of a given structure in space. The latter is the ratio of the relaxation time of the adaption of the structure to equilibrium and the time of the measuring experiment (time of observation). By introducing these parameters a better and more clear-cut definition can be given of amorphous solids, glassy or vitreous solids, real, “nearly” perfect and perfect crystals. A diagram can be drawn showing the relations between the various states of matter (including amorphous and vitreous states) as a function of the Repeatability Number and the Deborah Number. The relation between the Deborah Number and the Critical Cooling Rate is also discussed.

J.M. Stevels

Papers

The structure of borosilicate glasses studied by Raman scattering

Hydration of tricalcium silicate

Raman scattering measurements of silicate glasses and compounds

Nucleation kinetics and critical cooling rate of glass-forming liquids

Repeatability number, Deborah number and critical Cooling Rates as characteristic parameters of the vitreous state