Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

The making of portland cement

Q. How is portland cement made?


A. The raw materials are finely ground, intimately mixed, and heated to the beginning of fusion (about 1480ºC), usually in rotary kilns, which may be more than 210 m in length and 5 m in diameter. The partially fused (sintered) material that emerges from the kiln is portland cement clinker in roughly round particles up to the size of golf balls. The clinker is cooled and ground to a very fine powder, which is portland cement. During grinding, a small amount (about 2 to 5% by mass) of calcium sulfate (gypsum) is added to control the setting properties. For air-entraining cements, the air-entraining addition is interground at this time.


References:  SP-1(02); ACI 225R-19; E3-13

Topics in Concrete: Cementitious Material; Concrete Fundamentals

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