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Types of Portland cement

Portland Cement is the most common form of cement used for general purposes. It is produced from firing a mixture of clay or shale, and limestone or chalk. The clinker produced in the kiln is ground to a fine dust. Historically it was known as Ordinary Portland Cement (OPC) but with current standard BS EN 197-1 the closest classification would be CEMI (typically 42,5R or 52,5N).

Portland cement that is modified by further grinding to hydrate more rapidly in the first few hours after casting was historically known as Rapid Hardening Portland Cement (RHPC) and is no longer produced. As it stands the closest classification available would be a CEMI 52,5R. It is of particular use to manufacturers of precast concrete products because it allows greater productivity.

Sulfate Resisting Portland Cement (SRC) is Portland cement that is modified  to have a greater resistance to sulfate attack than Portland cement. It is often used on buried concrete structures in contact with grounds containing sulfates. No longer produced in the UK (with no available standard) it resistance can be achieved to a BS 8500 sulfate design class (DC) by using a particular CEMI,  a Portland Composite Cement or an equivalent mixer combination incorporating ggbs, fly ash or even a ternary blend with a +SR classification.

White Portland Cement is Portland cement that is white in colour rather than grey. Because care is needed in the choice of ingredients and in the manufacturing process to ensure the white colour, it is considerably more expensive than Portland cement and often requires the kiln to operate at higher temperature resulting in increased CO2 emissions. White cement is used for concretes where colour is particularly important.


Acknowledgement: The Concrete Society


Other references:CARDINAL, N. New Cement Standard. Concrete, Vol.55, No.6, July 2021, pages 36-28.