Calcium monoaluminate

M. A., Taylor L. A., and Wood J. A. (2002) The first known natural occurrence of calcium monoaluminate, in a calcium-aluminum-rich inclusion from the CH chondrite northwest Africa 470. Meteorit. Planet. Sci. 37, 1337-1344. 

Portland cement and high-alumina cements contain, in addition to calcium silicate phases, calcium monoaluminate, CaAl204 (or CA in cement chemist s shorthand, where C = CaO and A = AI2O3). The Al NMR spectra of this compound, in which the Al is exclusively in tetrahedral coordination, and a number of other calcium alu-minates have been determined (Muller et al. 1986), and more recently, using satellite transition spectroscopy (SATRAS) which has allowed the multiple tetrahedral sites in the various calcium aluminates to be distinguished (Skibsted et al. 1993). The NMR parameters for the synthetic aluminates and a number of their hydration products are shown in Table 5.4. 

The principal component present in CAC is calcium monoaluminate (CA in cement chemistry nomenclature, see Table 2.3). Its structure resembles that of P-tridymite, one of the polymorphs of Si02. Rather than having [SiOJ" " tetrahedral sharing corners in CA we have [AlOJ tetra-hedra. The large Ca ion distorts the tridymite network and the structure is monoclinic. 

The nucleation stage is shortened significantly when the calcium monoaluminate phase is contaminated with traces of C,2A2 [126]. In the presence of C,2A2 the concentration of Ca + in the hquid phase increases and the metastable region is attained, where the supersaturation in relation to C2AHg (point M in Fig. 3.45) takes place and the curve corresponding to the liquid phase composition is intersecting the curve of oversaturation which causes the instantaneous nucleatioa The induction period is then markedly reduced. The similar effect is observed when the... 

In type M, just as in type K cement, the matrix of the hardened paste is produced by the hydration of the existing Portland cement. Ettringite, the phase responsible for expansion, is formed in a reaction of calcium monoaluminate (CA), the main constituent of high-alitmina cemerrt, with calcium sulfate and calcium hydroxide, formed in the hydration of Portland cement and also added to the system as a constituent of the expansive additive ... 

The catalysts were prepared by mixing hydrozocarbonates of metals (MHO with calcium monoaluminate (CaAl204), calcium dialuminate (CaAUO ) or high alumina cement (CaAl204 + (laAl407) in aqueous or ammonia-aqueous medium. Phase composition and dispersity of the catalysts at different steps of the preparation were determined by X-ray diffraction... 

Calcium Monoaluminate. Ca0.Al203 melts incongruently at 1602 5 °C thermal expansion (0-1200 °C), 6.8 x 10- . A major constituent of high-alumina CEMENT (q.v.). 

The principal cementing compound in CAC is calcium monoaluminate (CA) present in amounts up to 60%. CA2 are... 

Calcium monoaluminate reacts rapidly with water as follows ... 

Calcium aluminate cements (CAC) have a wide range of alumina content (38 to 90%). The chemistry and principle cement-water reactions for high alumina cement—a widely used non-portland eement—are described in detail in Ch. 9. The primary binding phase is calcium monoaluminate (CaAl204 or CA). Refractory cements contain higher alumina contents (70 to 90%). 

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