PORTLAND CEMENT
Chemical composition.
Portland Cement is made up of four main compounds: tricalcium silicate (3CaOSiO2), dicalcium silicate (2CaOSiO2), tricalcium aluminate (3CaOAl2O3), and a tetra-calcium aluminoferrite (4CaO Al2O3Fe2O3). In an abbreviated notation differing from the normal atomic symbols, these compounds are designated as C3S, C2S, C3A, and C4AF, where C stands for calcium oxide (lime), S for silica, A for alumina, and F for iron oxide. Small amounts of uncombined lime and magnesia also are present, along with alkalies and minor amounts of other elements
Hydration.
The most important hydraulic constituents are the calcium silicates, C2S and C3S. Upon mixing with water, the calcium silicates react with water molecules to form calcium silicate hydrate (3CaO 2SiO23H2O) and calcium hydroxide (Ca [OH] 2). These compounds are given the shorthand notations C-S-H (represented by the average formula C3S2H3) and CH, and the Hydration reaction......
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