Cement types
Cement is a hydraulic binder: from the chemical reaction of a finely ground inorganic substance with water, an artificial mineral, cement brick, is created. The finer the cement powder, the faster this chemical reaction takes place (hydration). Hydration is an exothermic reaction, i.e. heat is released. Hardening occurs both under water and in air, the reaction product retains its strength and stability after hardening.
Cement types
There are different cement types, designated CEM I to CEM V, with a smaller or larger content of Portland cement and blast furnace slag or fly ash.
- CEM I : Portland cement with up to 5% other substances.
- CEM II : various mixtures of Portland cement with, for example, shale, fly ash, blast furnace slag, pozzolana… minimum 65% Portland cement.
- CEM III : blast furnace/portland cement mixture in 3 classes: A,B and C; where CEM III/A contains the least (40%) and CEM III/C the most (90%) blast furnace slag.
- CEM IV :pozzolanic cements (this type of cement is not produced in Belgium).
- CEM V :composite cements, with mixtures of Portland cement, blast furnace slag and pozzolans.
Cements are denoted by CEM followed by the number of the main type in Roman numerals. This is followed by a slash followed by the letters A,B or C (= decreasing clinker content). The designation may be followed by a horizontal stroke and a capital letter indicating the constituent used in addition to the Portland cement clinker.
Example: CEM II/B-M (S-V-L) 32.5R
Downloads of certificates
Click here to go to our downloads. Click here to go to our downloads. Here you will find certificates, declarations of performance (DOP) and the Safety Data Sheet (SDS) related to our cement types.
Special cement types
Certain cement types are used to manufacture concrete subjected to severe exposure or special environmental conditions.
For example, in damp environments (concrete that is continuously wet and where aggregates sensitive to alkalis are present), acidic environments (farms) or concrete subject to regular use of de-icing salts.
VVM has developed a CEM III/B 42.5N LH/SR CE LA for this purpose:
- LA (Low alkali)
- SR (Suphate resistant)
This cement contains a fairly high content of blast furnace slag.
Cement strengths
The strength development of a cement is determined not only by its composition but also by its grinding fineness.
Classification into classes (32.5 – 42.5 – 52.5) is based on a pressure test after 28 days. Within each strength class, young-age performance determines the distinction between the ‘Normal’ (N) and ‘Fast’ (R) versions. Mortar prisms are based on a standard ratio of cement, water and sand.
The strength rating of cement has only limited influence on the strength to be achieved in concrete or mortars. This is because a concrete mix can be made with, among other things, a lower water-cement factor (ratio of cement to water) than the mortar mix, which is used for the strength classification of cement. The structure of the aggregate also affects the final strength of concrete. Therefore, the strength class of cement cannot be directly traced back to a maximum strength class for concrete or mortar.
Class 32.5 is recommended for applications where high initial strength is not required, at average ambient temperatures (10° – 15°C) and structures of common thickness (< 50 cm).
Cements with strength class 42.5 are commonly used in cases where the required compressive strength of concrete at 28 days must exceed 30 N/mm² (i.e. higher than class C25/30 according to NBN B 15-001). These cements are also suitable for use at lower temperatures.
Class 52.5 is used for applications requiring an even higher initial strength than Class 42.5. E.g. for rapid stripping of prefabricated elements.