Ordinary Portland Cement (OPC) is one of the most commonly used types of cement in construction. It is a basic type of cement used for general construction purposes when there is no exposure to sulfates in the soil or groundwater.
Key Features of OPC:
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High compressive strength: Provides strong concrete.
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Fast setting: Gains strength quickly, especially in the first 28 days.
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Versatility: Suitable for a wide range of construction works.
Composition of OPC:
Typical components include:
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Lime (CaO) – 60–65%
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Silica (SiO₂) – 17–25%
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Alumina (Al₂O₃) – 3–8%
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Iron oxide (Fe₂O₃) – 0.5–6%
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Magnesia (MgO) – 0.1–4%
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Sulphur trioxide (SO₃) – 1–3%
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Gypsum (CaSO₄·2H₂O) – added to control the setting time
Grades of OPC (as per IS 269:2015):
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OPC 33 Grade – Minimum compressive strength of 33 MPa after 28 days.
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OPC 43 Grade – Minimum 43 MPa after 28 days.
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OPC 53 Grade – Minimum 53 MPa after 28 days.
Applications:
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Residential and commercial buildings
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Pavements and bridges
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Precast concrete products
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Plastering and masonry work
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General civil engineering works
Advantages:
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Readily available
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Cost-effective for general use
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Good workability and strength
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Compatible with most admixtures
Disadvantages:
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Not suitable for sulfate-rich environments (use Sulphate Resisting Cement instead)
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Higher heat of hydration (may lead to cracks in large pours)
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