White Portland cement

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White Portland cement or white ordinary Portland cement (WOPC) is similar to ordinary, gray Portland cement in all aspects except for its high degree of whiteness. Obtaining this color requires substantial modifications to the method of manufacturing. It requires a much lower content in colored impurities in the raw materials (essentially limestone and clay) used to produce clinker: low levels of Cr₂O₃, Mn₂O₃, and Fe₂O₃), but above all, a higher temperature is needed for the final sintering step in the cement kiln (1600 to 1700 °C in place of 1450 °C for ordinary Portland cement) because of the higher melting point of the mix depleted in iron oxides (serving as flux in Portland cement). Because of this, the process is more energy demanding and the white cement is somewhat more expensive than the gray product.