The raw material, which includes calcium oxide (CaO), silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃), is first ground into a fine powder and then partially melted. This process results in a hydraulic gelling substance primarily composed of calcium silicate. The content of calcium silicate in the mineral composition must be at least 66%, and the mass ratio of calcium oxide to silicon dioxide should not be less than 2.0.
Portland Cement (PO)
Strength Grades
Portland cement is available in six strength grades: 42.5, 42.5R, 52.5, 52.5R, 62.5, and 62.5R. These grades indicate the compressive strength of the cement after 28 days of curing. The "R" designation stands for "rapid hardening," meaning that the cement achieves higher early strength compared to its non-R counterpart.
Ordinary Portland Cement (OPC) has four strength grades: 42.5, 42.5R, 52.5, and 52.5R. It is commonly used in general construction applications where moderate strength and durability are required.
Slag Portland Cement, Pozzolanic Portland Cement, Fly Ash Portland Cement, and Composite Portland Cement are available in three main strength grades: 32.5, 32.5R, 42.5, 42.5R, 52.5, and 52.5R. These cements are typically blended with industrial by-products such as slag, fly ash, or pozzolanic materials, which enhance their workability, reduce heat of hydration, and improve long-term performance.
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