Chemical Composition of Cement

Chemical Composition of Cement

1. Main Components:

   • Calcium Oxide (CaO): Major component, approximately 60-65%. Derived from limestone or chalk.
   • Silica (SiO₂): Makes up 20-25%. Sourced from clay or shale.
   • Alumina (Al₂O₃): Constitutes 5-8%. Comes from bauxite or recycled alumina.
   • Iron Oxide (Fe₂O₃): Around 2-6%. Typically acquired from iron ore or recycled iron.
   • Magnesium Oxide (MgO): Present in small quantities, 0.5-4%. Sourced from dolomite.

2. Minor Components:

   • Sulfur Trioxide (SO₃): 1-3%. Contributes to clinker strength. Sourced from gypsum.
   • Alkalis (Na₂O and K₂O): Less than 1%. Affects the chemical properties and setting time. Derived from various raw materials.

3. Additional Compounds:

   • Calcium Sulfate (CaSO₄): Regulates setting time of cement.
   • Tricalcium Silicate (C₃S): Provides early strength.
   • Dicalcium Silicate (C₂S): Offers strength over a longer curing period.
   • Tricalcium Aluminate (C₃A): Contributes to early set and heat generation.
   • Tetracalcium Aluminoferrite (C₄AF): Influences color and assists in the workability of cement.

4. Hydration Reaction:

   • Reacts with water to form products such as calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)₂).
   • These products lead to the hardening of cement.

5. Significance:

   • Proportions of these compounds: Influence the properties like strength, setting time, and durability.
   • Quality control: Essential to ensure cement consistency and performance for construction purposes.

Study these notes to understand the fundamental components and their roles in the chemical composition of cement, which directly relates to its performance in construction.