Constituents of Portland Cement

Portland cement is a key ingredient in construction, known for its strength and versatility. Here, we'll explore the raw materials used to make it, their functions, and the impact of excess quantities.

Constituents of Portland Cement

Key Oxides and Their Average Percentages

• Lime (CaO): 63%
• Silica (SiO₂): 20.1%
• Alumina (Al₂O₃): 6.1%
• Iron Oxide (Fe₂O₃): 3.1%
• Magnesia (MgO): 2.1%
• Alkalis (Na₂O + K₂O): 1%
• Sulphur Trioxide (SO₃): 1.5%

Functions and Effects of Key Oxides

Oxide	Compound (%)	Avg (%)	Function	Excess Quantity Effects
Lime (CaO)	60-65	63	Controls strength, soundness, efficiency.	Unsoundness
Silica (SiO₂)	17-25	20.1	Contributes to strength.	Causes slow setting
Alumina (Al₂O₃)	3-8	6.1	Helps in quick setting.	Lowers strength
Iron Oxide (Fe₂O₃)	0.5-6	3.1	Provides color and fuses ingredients, acts as flux.	Causes same issues
Magnesia (MgO)	0.5-4	2.1	Imparts color and hardness.	Leads to cracks and makes cement unsound
Alkalis (Na₂O + K₂O)	0.5-1	1	Leaves residues.	Causes efflorescence and cracks
Sulphur Trioxide (SO₃)	1-2	1.5	-	Makes cement unsound

Conclusion

1. Strength & Responsibility: Lime, Silica
2. Quick Setting: Alumina
3. Hardness: Iron Oxide, Magnesia
4. Residues: Alkalis, Sulphur Trioxide

Presentation of Constituents of Portland Cement