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Belite is the mineral in Portland cement responsible for development of "late" strength. The other silicate, alite contributes "early" strength, due to its higher reactivity. Belite reacts with water (roughly) to form calcium silicate hydrates (C-S-H) and portlandite (Ca(OH) 2) according to the reaction:
Alite is the major phase in Portland cement responsible for setting and development of "early" strength. The other silicate, belite contributes "late" strength, due to its lower reactivity. Alite is more reactive because of its higher Ca content, and the presence of an oxide ion in the lattice.
1300 to 1450 °C – partial (20–30%) melting takes place, and belite reacts with calcium oxide to form alite (Ca 3 O·SiO 4) (also known as C3S in the Cement Industry). Typical clinker nodules Alite is the characteristic constituent of Portland cement .
Rawmixes are formulated to contain a correctly balanced chemistry for the production of calcium silicates (alite and belite) and fluxes (aluminate and ferrite) in the kiln. Chemical analysis data in cement manufacture are expressed in terms of oxides, and the most important of these in rawmix design are SiO 2 , Al 2 O 3 , Fe 2 O 3 and CaO.
The materials in cement clinker are alite, belite, tricalcium aluminate, and tetracalcium alumino ferrite. The aluminium, iron, and magnesium oxides are present as a flux allowing the calcium silicates to form at a lower temperature, [ 15 ] and contribute little to the strength.
Upon addition of water, clinker minerals react to form different types of hydrates and "set" (harden) as the hydrated cement paste becomes concrete.The calcium silicate hydrates (C-S-H) (hydrates of alite and belite minerals) represent the main "glue" components of the concrete.
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Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar, and many plasters. [43] It consists of a mixture of calcium silicates (alite, belite), aluminates and ferrites—compounds, which will react with water.