What is cement?

According to PN-EN 197-1 standard cement, called CEM, is a hydraulic binding agent i.e. finely ground inorganic material. When mixed with water, this material makes a grout with binding properties, which hardens as a result of reactions and hydrating processes and becomes durable and resistant, also underwater. When properly weighed and mixed with aggregates and water, PN-EN 197-1 cement should make concrete or mortar, which remain workable for a relatively long period of time and after a specified time they should gain proper strength and keep long-term volume stability.


Cement composition might include:

  • main components – specially selected inorganic materials, whose share in relation to the total of all main and secondary components exceeds 5.0 % of the total mass
  • secondary components - specially selected inorganic materials, whose share in relation to the total of all the main and secondary components does not exceed 5.0 % of the total mass
  • calcium sulphate – it is added to other components during the cement production process to control the setting time. Calcium sulphate might occur as gypsum, hemihydrate and anhydrite, or a mixture of those. The naturally occurring ones are gypsum and anhydrite. Calcium sulphate comes also as a bi-product of some industrial production processes.
  • Admixtures – they are used to improve either the production process or cement properties. The total amount of admixtures should not exceed 1.0 % of the cement mass (excluding colours). Admixtures must not add to corrosion processes of reinforcement elements, or affect the properties of concrete or mortar made from cement. When concrete, mortar or grout admixtures are added to cement according to the EN 934 standard, then their packaging or the specification accompanying a delivery should carry the standardized name of the admixture(s) used.

 

 Cement main components
Portland clinker (K)
Granulated blastfurnace slag (S)
Pozzolana (PQ)
Fly ash (V, W)
Burnt shale (T)
Limestone (L, LL)
Silica fume (D)

Cement type and composition
CEM I –   PORTLAND CEMENT
CEM II –  PORTLAND-COMPOSITE        CEMENT
CEM III – BLAST FURNACE CEMENT
CEM IV – POZZOLANIC CEMENT
CEM V –  COMPOSITE CEMENT

Due to many different admixtures used, cements are divided into three varieties: A, B and C.

Cement strength classes
Depending on compressive strength evaluated after 28 days and designated according to PN-EN 196 1, cement has been divided into three compressive classes (compressive strength expressed in N/mm2; 1 MPa=1 N/mm2):
class 32.5;         class 42.5,         class 52.2

With reference to their early strength development these three classes comprise cement subclasses of high early strength (marked with letter R):
32.5 R,     42.5 R,        52.5 R

and cement subclasses of normal early strength (marked with letter N)
32.5 N,     42.5 N,        52.5 N

Additionally, PN-EN 197-4 standard “Cement. Part 4: composition, specifications and conformity criteria for low early strength blast furnace cements” introduces three strength subclasses for blast furnace cements of low early strength (marked with letter L):
32.5 L,     42.5 L,        52.5 L

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