Which one of the following is NOT present in cement ?

Portland cement is primarily composed of four major mineral phases known as Bogue's compounds. These include Tricalcium silicate (3CaO·SiO2 or C3S), which provides early strength; Dicalcium silicate (2CaO·SiO2 or C2S), which contributes to long-term strength; and Tricalcium aluminate (3CaO·Al2O3 or C3A), which is responsible for early setting [1]. The fourth major compound is Tetracalcium aluminoferrite (4CaO·Al2O3·Fe2O3 or C4AF). While calcium silicates are fundamental, they exist specifically in the dicalcium and tricalcium forms. Tetracalcium silicate (4CaO·SiO2) is not a standard constituent of Portland cement clinker. The chemical composition is carefully balanced using raw materials like limestone (calcium oxide) and silica to ensure these specific phases form during the sintering process. Therefore, 4CaO·SiO2 is the compound not present in cement.

Sources

1. [1] https://www.sciencedirect.com/science/article/am/pii/S2666549221000141