Alite origin

An alternative to silicate-based Portland cement is the calcium aluminate cement, ciment fondu, which originated with the Lafarge company in France in 1908. Ciment fondu is typically made by heating limestone with bauxite, which is mainly AIO(OH) but contains much iron oxide (see Section 17.2). As noted above, calcium aluminate hydrates and hardens much more rapidly than alite, and so ciment fondu, either as such or mixed with Portland cement, can be used whenever a rapidly setting cement is required, for example, for construction at low temperatures. Concretes made from aluminate cements remain serviceable at higher temperatures than Portland cements and so are used to make cast refractories for pyrometal-lurgical applications. 

Belite inclusions in alite Relatively large (12 to 13 pm) In clinker made with quartz sand 8 pm in clinker made with sponge-silica (Dorn, 1980) residual original belite (Brown, 1948)... 

Photograph 7-82 Free lime in clinker thin section. Crystals exhibit prominent cubic cleavage characteristic of free lime. An abundance of free-lime nests (some showing original limestone particle outline), anhedral alite, and extremely nonuniform distribution of silicates suggests poorly mixed coarse feed. Dry-process kiln, coal fired. (S A6700)... 

This section shows observations on later-age pastes. Alite and cement pastes hydrated for 90 days, at 20°C with w/c = 0.4, are shown in Figure 8.49a and b, respectively. Both inner product (IP) C-S-H regions and fibrillar outer product (OP) C-S-H are visible. As the alite sample (Figure 8.49a) is devoid of aluminate phases, only C-S-H and CH form. In cement systems (Figure 8.49b) relics from AFt or AFm particles removed during preparation are visible close to the border of the original alite grain. 

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