Cement chemistry

When mature concrete is contaminated by chloride, e.g. by contact with deicing salts, the cement chemistry is more complex, and less chloride is taken up by the cement hydrate minerals and a larger proportion is free in the pore solutions and can therefore pose a greater hazard. When embedded steel corrodes, the production of a more voluminous corrosion product pushes the concrete from the steel with resultant cracking and spalling of the concrete. 

The solvation (hydration) and desolvation of ions is important to the gelation process in AB cement chemistry. The large dipole moment of ion-pairs causes them to interact with polar molecules, including those of the solvent. This interaction can be appreciable. Much depends on whether the solvent molecule or molecules can intrude themselves between the two ions of the ion-pair. Thus, hydration states can affect the magnitude of the interaction. The process leading to separation of ions by solvent molecules was perceived by Winstein et al. (1954) and Grunwald (1954). 

Crisp, S., Lewis, B. G. Wilson, A. D. (1976d). Glass-ionomer cements chemistry of erosion. Journal of Dental Research, 55, 1032-41. 

Clusters of modules (from JME) on selected topics such as polymer experiments or cement chemistry are available as short textbooks. 

The sensitivity of Magnetic Resonance (MR) to the local concentration, molecular dynamics and molecular environment of these nuclei make it well suited for the study of deterioration processes in concrete materials. Hydrogen (water), lithium, sodium, chlorine and potassium are all MR sensitive nuclei and play an important role in cement chemistry. The ability of MRI to spatially resolve and non-destructively examine test samples as a function of treatment or exposure has the potential to provide new insight to better understand deterioration mechanisms and mass transport properties of concrete materials. 

It is important to note that one of the greatest obstacles the builders had to overcome was concrete and cement chemistry. 

Taylor, H. F. W. 1990. Cement Chemistry. Academic Press, New York, NY. 

Taylor, H. Cement Chemistry, London Academic Press, 1990. 

The trace element compositions of the four major cement zones are shown in Figure 8.28 and Table 8.5. It is evident that each zone is chemically distinct. Zone 1 is rich in Mg and poor in Mn and Fe Zone 2 is rich in Mn and has intermediate concentrations of Mg and Fe Zone 3 is poor in all three trace elements and Zone 5 is rich in Fe and Mg and has intermediate concentrations of Mn. These trace element differences account for the luminescence differences among the cement zones. The distinct chemical signature of each zone supports the petrographic evidence that each zone records a regionally extensive cementation event in a distinct meteoric water chemistry. If the zones were lateral equivalents of each other rather than separate time-stratigraphic events, one would anticipate considerable overlap between the zonal cement chemistries. 

That is due to its higher inner surface, i.e., like a fme sponge (here cement mortar) can absorbe more water than a course one (here lime mortar). W. Czemin, Zementchemie fiir Bauingenieure, Bauverlag, Wiesbaden 1977, p. 49f. (Engl. Cement chemistry and physics for civil engineers, ibid., 1980) cf. my report (note 19), chapter 2.5. 

Chemical formulae in cement chemistry are often expressed as a sum of oxides thus tricalcium silicate, CajSiO, can be written as 3Ca0 Si02- This does not imply that the constituent oxides have any separate existence within the structure. It is usual to abbreviate the formulae of the commoner oxides to single letters, such as C for CaO or S for SiOj, CajSiOj thus becoming CjS. This system is often combined with orthodox chemical notation within a chemical equation, e.g. 

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