Reducing clinker content

Cement types are regulated through EN 197-1 containing 27 different types. The most important being CEM I, II and III in terms of production figures (see Figure 1 and Figure 2). There are basically two ways of mixing Portland clinker and mineral additions in order to reduce the clinker content in the binder:

• At the cement plant by the cement producer obtaining blended cements (CEM II - CEM V). This method seems to be increasing especially in the central and southern part of Europe.
  
• At the concrete plant where CEM I is mixed with fly ash, silica fume, slag, etc. in the concrete mixer by the concrete manufacturer.

Actually other combinations also exist such as mixing of different cement types (e.g. CEM I and CEM III) or mixing of blended cement with mineral additions in the concrete mixer. The former being used in the Netherlands and the latter being allowed for in Sweden.

There can be stated several pro's and con's for the different methods but in the end it all comes down to the traditions and experiences in each country. One method puts the responsibility of the binder composition into the hands of the cement producer and the other gives more flexibility to the concrete producer to design the type of concrete to meet the specifications. Thus, both of the methods can be termed best available technology when it comes to reducing the clinker amount in an efficient way.

More information on this subject can be found under "Production and application of blended cements".

Figure 1: Cement production distributed on cement type and strength class. The numbers on the columns indicate the share of CEM I and CEM II within each strength class.
Source: CEMBUREAU 2001 production figures.

Figure 2: Development of cement production figures in CEMBUREAU member countries. Taken from Cluster 2 presentation.

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