Which one among the following is the main ingredient in cement ?

Limestone is the primary and most essential raw material used in the production of cement. It serves as the main source of calcium carbonate (CaCO3), which provides the necessary calcium oxide (lime) for the chemical reactions that occur during the manufacturing process [t1][t3]. In the production of Portland cement, limestone typically accounts for approximately 70% to 80% of the raw material mix [t9]. It is considered the basic raw material for the cement industry [c3]. Other ingredients like clay provide silica, alumina, and iron oxide, while gypsum is added in smaller quantities (usually 3-5%) to control the setting time of the cement [t3][t7]. Ash (such as fly ash) can be used as an alternative or supplementary material, but limestone remains the fundamental ingredient required to form the clinker [t1][t5].

Sources

1. [1] NCERT. (2022). Contemporary India II: Textbook in Geography for Class X (Revised ed.). NCERT. > Chapter 5: Print Culture and the Modern World > Rock Minerals > p. 111